---
layout: page
title: API
permalink: /API/
---

* toc
{:toc}

# jerry_run_simple

**Summary**
The simplest way to run JavaScript.

**Prototype**

```c
jerry_completion_code_t
jerry_run_simple (const jerry_api_char_t *script_source,
                  size_t script_source_size,
                  jerry_flag_t flags);
```

- `script_source` - source code;
- `script_source_size` - size of source code buffer, in bytes;
- returned value - completion code that indicates whether run was performed successfully (`JERRY_COMPLETION_CODE_OK`), or an unhandled JavaScript exception occurred (`JERRY_COMPLETION_CODE_UNHANDLED_EXCEPTION`).

**Example**

```c
{
  const jerry_api_char_t *script = "print ('Hello, World!');";

  jerry_run_simple (script, strlen ((const char *) script), JERRY_FLAG_EMPTY);
}
```

**See also**

- [jerry_init](#jerry_init)
- [jerry_cleanup](#jerry_cleanup)
- [jerry_parse](#jerry_parse)
- [jerry_run](#jerry_run)

# jerry_init

**Summary**

Initializes JerryScript engine, making possible to run JavaScript code and perform operations on JavaScript values.

**Prototype**

```c
void
jerry_init (jerry_flag_t flags);
```

`flags` - combination of various engine configuration flags:

- `JERRY_FLAG_EMPTY` - no flags, just initialize in default configuration;
- `JERRY_FLAG_SHOW_OPCODES` - print compiled byte-code;
- `JERRY_FLAG_MEM_STATS` - dump memory statistics;
- `JERRY_FLAG_MEM_STATS_SEPARATE` - dump memory statistics and reset peak values after parse;
- `JERRY_FLAG_ENABLE_LOG` - enable logging;

**Example**

```c
{
  jerry_init (JERRY_FLAG_ENABLE_LOG);

  // ...

  jerry_cleanup ();
}
```

**See also**

- [jerry_cleanup](#jerry_cleanup)

# jerry_cleanup

**Summary**

Finish JavaScript engine execution, freeing memory and JavaScript values.

JavaScript values, received from engine, are inaccessible after the cleanup.

**Prototype**

```c
void
jerry_cleanup (void);
```

**See also**

- [jerry_init](#jerry_init)

# jerry_parse

**Summary**
Parse specified script to execute in Global scope.

Current API doesn't permit replacement or modification of Global scope's code without engine restart,
so `jerry_parse` could be invoked only once between `jerry_init` and `jerry_cleanup`.

**Prototype**

```c
bool
jerry_parse (const jerry_api_char_t *source_p,
             size_t source_size,
             jerry_api_object_t **error_obj_p);
```
- `source_p` - string, containing source code to parse;
- `source_size` - size of the string, in bytes.
- `error_obj_p` - error object (output parameter)

**Example**

```c
{
  jerry_init (JERRY_FLAG_EMPTY);

  char script [] = "print ('Hello, World!');";
  size_t script_size = strlen ((const char *) script);

  jerry_api_object_t *error_object_p = NULL;
  if (!jerry_parse (script, script_size, &error_object_p))
  {
    /* Error object must be freed, if parsing failed */
    jerry_api_release_object (error_object_p);
  }

  jerry_cleanup ();
}
```

**See also**

- [jerry_run](#jerry_run)


# jerry_parse_and_save_snapshot

**Summary**

Generate snapshot from the specified source.

**Prototype**

```c
size_t
jerry_parse_and_save_snapshot (const jerry_api_char_t *source_p,
                               size_t source_size,
                               bool is_for_global,
                               uint8_t *buffer_p,
                               size_t buffer_size);
```

- `source_p` - script source
- `source_size` - script source size
- `is_for_global` - snapshot would be executed as global (true) or eval (false)
- `buffer_p` - buffer to save snapshot to
- `buffer_size` - the buffer's size
- return value
  - the size of snapshot, if it was generated succesfully (i.e. there are no syntax errors in source code, buffer size is sufficient, and snapshot support is enabled in current configuration through JERRY_ENABLE_SNAPSHOT)
  - 0 otherwise

**Example**

```c
{
  jerry_init (JERRY_FLAG_EMPTY);

  static uint8_t global_mode_snapshot_buffer[1024];
  const char *code_to_snapshot_p = "(function () { return 'string from snapshot'; }) ();";

  size_t global_mode_snapshot_size = jerry_parse_and_save_snapshot ((jerry_api_char_t *) code_to_snapshot_p,
                                                                    strlen (code_to_snapshot_p),
                                                                    true,
                                                                    global_mode_snapshot_buffer,
                                                                    sizeof (global_mode_snapshot_buffer));
}
```

**See also**
- [jerry_init](#jerry_init)
- [jerry_exec_snapshot](#jerry_exec_snapshot)


# jerry_run

**Summary**
Run code of Global scope.

The code should be previously registered through `jerry_parse`.

**Prototype**

```c
jerry_completion_code_t
jerry_run (jerry_api_value_t *error_value_p);
```
- `error_value_p` - error value (output parameter)
- returned value - completion code that indicates whether run performed successfully
  - `JERRY_COMPLETION_CODE_OK` - successful completion
  - `JERRY_COMPLETION_CODE_UNHANDLED_EXCEPTION` - an unhandled JavaScript exception occurred
  - `JERRY_COMPLETION_CODE_INVALID_SNAPSHOT_VERSION` - snapshot version mismatch
  - `JERRY_COMPLETION_CODE_INVALID_SNAPSHOT_FORMAT` - snapshot format is not valid

**Example**

```c
{
  const jerry_api_char_t script[] = "print ('Hello, World!');";
  size_t script_size = strlen ((const char *) script);

  /* Initialize engine */
  jerry_init (JERRY_FLAG_EMPTY);

  /* Setup Global scope code */
  jerry_api_object_t *error_object_p = NULL;
  if (!jerry_parse (script, script_size, &error_object_p))
  {
    /* Error object must be freed, if parsing failed */
    jerry_api_release_object (error_object_p);
  }
  else
  {
    /* Execute Global scope code
     *
     * Note:
     *      Initialization of 'error_value' is not mandatory here.
     */
    jerry_api_value_t error_value = jerry_api_create_void_value ();
    jerry_completion_code_t return_code = jerry_run (&error_value);

    if (return_code == JERRY_COMPLETION_CODE_UNHANDLED_EXCEPTION)
    {
      /* Error value must be freed, if 'jerry_run' returns with an unhandled exception */
      jerry_api_release_value (&error_value);
    }
  }

  jerry_cleanup ();
}
```

**See also**

- [jerry_parse](#jerry_parse)


# jerry_exec_snapshot

**Summary**

Execute snapshot from the specified buffer.

**Prototype**

```c
jerry_completion_code_t
jerry_exec_snapshot (const void *snapshot_p,
                     size_t snapshot_size,
                     bool copy_bytecode,
                     jerry_api_value_t *retval_p);
```
- `snapshot_p` - pointer to snapshot
- `snapshot_size` - size of snapshot
- `copy_bytecode` - flag, indicating whether the passed snapshot buffer should be copied to the engine's memory. If set the engine should not reference the buffer after the function returns (in this case, the passed buffer could be freed after the call). Otherwise (if the flag is not set) - the buffer could only be freed after the engine stops (i.e. after call to jerry_cleanup).
- `retval_p` - returned value (ECMA-262 'undefined' if code is executed as global scope code
- return value - completion code

**Example**

```c
{
  bool is_ok;
  jerry_api_value_t res;
  static uint8_t global_mode_snapshot_buffer[1024];
  const char *code_to_snapshot_p = "(function () { return 'string from snapshot'; }) ();";

  jerry_init (JERRY_FLAG_EMPTY);
  size_t global_mode_snapshot_size = jerry_parse_and_save_snapshot ((jerry_api_char_t *) code_to_snapshot_p,
                                                                    strlen (code_to_snapshot_p),
                                                                    true,
                                                                    global_mode_snapshot_buffer,
                                                                    sizeof (global_mode_snapshot_buffer));
  jerry_cleanup ();

  jerry_init (JERRY_FLAG_EMPTY);

  is_ok = (jerry_exec_snapshot (global_mode_snapshot_buffer,
                                global_mode_snapshot_size,
                                false,
                                &res) == JERRY_COMPLETION_CODE_OK);
}
```

**See also**

- [jerry_init](#jerry_init)
- [jerry_cleanup](#jerry_cleanup)
- [jerry_parse_and_save_snapshot](#jerry_parse_and_save_snapshot)


# jerry_get_memory_limits

**Summary**

Gets configured memory limits of JerryScript.

**Prototype**

```c
void
jerry_get_memory_limits (size_t *out_data_bss_brk_limit_p,
                         size_t *out_stack_limit_p);
```
- `out_data_bss_brk_limit_p` - out parameter, that gives the maximum size of data + bss + brk sections
- `out_stack_limit_p` - out parameter, that gives the maximum size of the stack

**Example**

```c
  jerry_init (JERRY_FLAG_EMPTY);

  size_t stack_limit;
  size_t data_dss_brk_limit;
  jerry_get_memory_limits(&stack_limit, &data_dss_brk_limit);
```

**See also**

- [jerry_init](#jerry_init)


# jerry_api_gc

**Summary**
Performs garbage collection.

**Prototype**

```c
void
jerry_api_gc (void);
```

**Example**

```c
jerry_api_gc ();
```


# jerry_api_value_t

**Summary**
The data type represents any JavaScript value that can be sent to or received from the engine.

Type of value is identified by `jerry_api_value_t::type`, and can be one of the following:

- `JERRY_API_DATA_TYPE_VOID` - no return value
- `JERRY_API_DATA_TYPE_UNDEFINED` - JavaScript undefined;
- `JERRY_API_DATA_TYPE_NULL` - JavaScript null;
- `JERRY_API_DATA_TYPE_BOOLEAN` - boolean;
- `JERRY_API_DATA_TYPE_FLOAT32` - number;
- `JERRY_API_DATA_TYPE_FLOAT64` - number;
- `JERRY_API_DATA_TYPE_UINT32` - number;
- `JERRY_API_DATA_TYPE_STRING` - string;
- `JERRY_API_DATA_TYPE_OBJECT` - reference to JavaScript object.

**Structure**

```c
typedef struct jerry_api_value_t
{
  jerry_api_data_type_t type;

  union
  {
    bool v_bool;

    float v_float32;
    double v_float64;

    uint32_t v_uint32;

    jerry_api_string_t v_string;
    jerry_api_object_t v_object;
  } u;
} jerry_api_value_t;
```

**See also**

- [jerry_api_eval](#jerry_api_eval)
- [jerry_api_call_function](#jerry_api_call_function)
- [jerry_api_construct_object](#jerry_api_construct_object)

# jerry_api_eval

**Summary**
Perform JavaScript `eval`.

**Prototype**

```c
jerry_completion_code_t
jerry_api_eval (const jerry_api_char_t *source_p,
                size_t source_size,
                bool is_direct,
                bool is_strict,
                jerry_api_value_t *retval_p);
```

- `source_p` - source code to evaluate;
- `source_size` - length of the source code;
- `is_direct` - whether to perform `eval` in "direct" mode (possible only if `eval` invocation is performed from native function, called from JavaScript);
- `is_strict` - perform `eval` as it is called from "strict mode" code;
- `retval_p` - value, returned by `eval` (output parameter);
- returned value - completion code that indicates whether run performed successfully (`JERRY_COMPLETION_CODE_OK`), or an unhandled JavaScript exception occurred (`JERRY_COMPLETION_CODE_UNHANDLED_EXCEPTION`).

**Example**

```c
{
  jerry_api_value_t ret_val;

  jerry_completion_code_t status = jerry_api_eval (str_to_eval,
                                                   strlen (str_to_eval),
                                                   false, false,
                                                   &ret_val);
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_create_external_function](#jerry_api_create_external_function)
- [jerry_external_handler_t](#jerry_external_handler_t)


# jerry_api_acquire_value

**Summary**

Acquires the specified Jerry API value.

For values of string and object types this acquires the underlying data, for all other types it is a no-op. The acquired pointer have to be released by [jerry_api_release_value](#jerry_api_release_value).

**Prototype**

```c
jerry_api_value_t *
jerry_api_acquire_value (jerry_api_value_t *value_p);
```
- `value_p` - pointer to an API value
- return value - pointer that may be used outside of the engine

**Example**

```c
{
  jerry_init (JERRY_FLAG_EMPTY);
  jerry_api_object_t *object_p = jerry_api_create_object();
  jerry_api_value_t object_value = jerry_api_create_object_value(object_p);

  jerry_api_value_t *acquired_object = jerry_api_acquire_value(&object_value);

  jerry_api_release_value(acquired_object);
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_release_value](#jerry_api_release_value)
- [jerry_api_acquire_string](#jerry_api_acquire_string)
- [jerry_api_acquire_object](#jerry_api_acquire_object)


# jerry_api_release_value

**Summary**
Release specified pointer to the value.

**Prototype**

```c
void
jerry_api_release_value (jerry_api_value_t *value_p);
```

- `value_p` - pointer to the value.

**Example**
```c
{
    jerry_api_value_t val1;
    jerry_api_value_t val2;

    val1.type = JERRY_API_DATA_TYPE_OBJECT;
    val1.u.v_object = jerry_api_create_object ();

    val2.type = JERRY_API_DATA_TYPE_STRING;
    val2.u.v_string = jerry_api_create_string ("abc");

    ... // usage of val1

    jerry_api_release_value (&val1);

    ... // usage of val2

    jerry_api_release_value (&val2);
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)


# jerry_api_create_string

**Summary**
Create new JavaScript string.

Upon the JavaScript string becomes unused, all pointers to it should be released using [jerry_api_release_string](#jerry_api_release_string).

**Prototype**

```c
jerry_api_string_t *
jerry_api_create_string (const jerry_api_char_t *v);
```

- `v` - value of string to create;
- returned value is pointer to created string.

**Example**

```c
{
  jerry_api_string_t *string_p = jerry_api_create_string ("abc");

  ...

  jerry_api_release_string (string_p);
}
```

**See also**

- [jerry_api_acquire_string](#jerry_api_acquire_string)
- [jerry_api_release_string](#jerry_api_release_string)
- [jerry_api_string_to_char_buffer](#jerry_api_string_to_char_buffer)

# jerry_api_string_to_char_buffer

**Summary**
Copy string characters to specified buffer, append zero character at end of the buffer.

**Prototype**

```c
jerry_api_size_t
jerry_api_string_to_char_buffer (const jerry_api_string_t *string_p,
                                 jerry_api_char_t *buffer_p,
                                 jerry_api_size_t buffer_size);
```

- `string_p` - pointer to a string;
- `buffer_p` - pointer to output buffer (can be NULL, is `buffer_size` is 0);
- `buffer_size` - size of the buffer;
- returned value:
  - number of bytes, actually copied to the buffer - if characters were copied successfully;
  - otherwise (in case size of buffer is insufficient) - negative number, which is calculated as negation of buffer size, that is required to hold characters.

**Example**

```c
{
  jerry_api_object_t *obj_p = jerry_api_get_global ();
  jerry_api_value_t val;

  bool is_ok = jerry_api_get_object_field_value (obj_p,
                                                 "field_with_string_value",
                                                 &val);

  if (is_ok)
  {
    bool is_string = (val.type == JERRY_API_DATA_TYPE_STRING);

    if (is_string)
    {
      // neg_req_sz would be negative, as zero-size buffer is insufficient for any string
      jerry_api_size_t req_sz = jerry_api_get_string_size (val.string_p);
      jerry_api_char_t *str_buf_p = (jerry_api_char_t *) malloc (req_sz);

      // sz would be -neg_req_sz
      jerry_api_size_t sz = jerry_api_string_to_char_buffer (val.string_p,
                                                             str_buf_p,
                                                             req_sz);

      printf ("%s", str_buf_p);

      free (str_buf_p);
    }

    jerry_api_release_value (&val);
  }

  jerry_api_release_object (obj_p);
}
```

**See also**

- [jerry_api_create_string](#jerry_api_create_string)
- [jerry_api_value_t](#jerry_api_value_t)

# jerry_api_acquire_string

**Summary**
Acquire new pointer to the string for usage outside of the engine.

The acquired pointer should be released with [jerry_api_release_string](#jerry_api_release_string).

**Prototype**

```c
jerry_api_string_t *
jerry_api_acquire_string (jerry_api_string_t *string_p);
```

- `string_p` - pointer to the string;
- returned value - new pointer to the string.

**Example**

```c
{
  jerry_api_string_t *str_ptr1_p = jerry_api_create_string ("abc");
  jerry_api_string_t *str_ptr2_p = jerry_api_acquire_string (str_ptr1_p);

  ... // usage of both pointers

  jerry_api_release_string (str_ptr1_p);

  ... // usage of str_ptr2_p pointer

  jerry_api_release_string (str_ptr2_p);
}
```

**See also**

- [jerry_api_release_string](#jerry_api_release_string)
- [jerry_api_create_string](#jerry_api_create_string)

# jerry_api_release_string

**Summary**
Release specified pointer to the string.

**Prototype**

```c
void
jerry_api_release_string (jerry_api_string_t *string_p);
```

- `string_p` - pointer to the string.

**Example**

```c
{
  jerry_api_string_t *str_ptr1_p = jerry_api_create_string ("abc");
  jerry_api_string_t *str_ptr2_p = jerry_api_acquire_string (str_ptr1_p);

  ... // usage of both pointers

  jerry_api_release_string (str_ptr1_p);

  ... // usage of str_ptr2_p pointer

  jerry_api_release_string (str_ptr2_p);
}
```

**See also**

- [jerry_api_acquire_string](#jerry_api_acquire_string)
- [jerry_api_create_string](#jerry_api_create_string)

# jerry_api_create_object

**Summary**
Create new JavaScript object, like with `new Object()`.

Upon the JavaScript object becomes unused, all pointers to it should be released using [jerry_api_release_object](#jerry_api_release_object).

**Prototype**

```c
jerry_api_object_t *
jerry_api_create_object ();
```

- returned value is pointer to the created object.

**Example**

```c
{
  jerry_api_object_t *object_p = jerry_api_create_object ();

  ...

  jerry_api_release_object (object_p);
}
```

**See also**

- [jerry_api_acquire_object](#jerry_api_acquire_object)
- [jerry_api_release_object](#jerry_api_release_object)
- [jerry_api_add_object_field](#jerry_api_add_object_field)
- [jerry_api_delete_object_field](#jerry_api_delete_object_field)
- [jerry_api_get_object_field_value](#jerry_api_get_object_field_value)
- [jerry_api_set_object_field_value](#jerry_api_set_object_field_value)
- [jerry_api_get_object_native_handle](#jerry_api_get_object_native_handle)
- [jerry_api_set_object_native_handle](#jerry_api_set_object_native_handle)

# jerry_api_acquire_object

**Summary**
Acquire new pointer to the object for usage outside of the engine.

The acquired pointer should be released with [jerry_api_release_object](#jerry_api_release_object).

**Prototype**

```c
jerry_api_object_t *
jerry_api_acquire_object (jerry_api_object_t *object_p);
```

- `object_p` - pointer to the object;
- returned value - new pointer to the object.

**Example**

```c
{
  jerry_api_object_t *obj_ptr1_p = jerry_api_create_object ();
  jerry_api_object_t *obj_ptr2_p = jerry_api_acquire_object (obj_ptr1_p);

  ... // usage of both pointers

  jerry_api_release_object (obj_ptr1_p);

  ... // usage of obj_ptr2_p pointer

  jerry_api_release_object (obj_ptr2_p);
}
```

**See also**

- [jerry_api_release_object](#jerry_api_release_object)
- [jerry_api_create_object](#jerry_api_create_object)

# jerry_api_release_object

**Summary**
Release specified pointer to the object.

**Prototype**

```c
void
jerry_api_release_object (jerry_api_object_t *object_p);
```

- `object_p` - pointer to the object.

**Example**

```c
{
  jerry_api_object_t *obj_ptr1_p = jerry_api_create_object ();
  jerry_api_object_t *obj_ptr2_p = jerry_api_acquire_object (obj_ptr1_p);

  ... // usage of both pointers

  jerry_api_release_object (obj_ptr1_p);

  ... // usage of obj_ptr2_p pointer

  jerry_api_release_object (obj_ptr2_p);
}
```

**See also**

- [jerry_api_acquire_object](#jerry_api_acquire_object)
- [jerry_api_create_object](#jerry_api_create_object)

# jerry_api_get_global

**Summary**
Get the Global object.

**Prototype**

```c
jerry_api_object_t *
jerry_api_get_global (void);
```

- returned value - pointer to the Global object.

Received pointer should be released with [jerry_api_release_object](#jerry_api_release_object), just when the value becomes unnecessary.

**Example**

```c
{
  jerry_api_object_t *glob_obj_p = jerry_api_get_global ();

  jerry_api_value_t val;
  bool is_ok = jerry_api_get_object_field_value (glob_obj_p, "some_field_name", &val);
  if (is_ok)
  {
    ... // usage of 'val'

    jerry_api_release_value (&val);
  }

  jerry_api_release_object (glob_obj_p);
}
```

**See also**

- [jerry_api_release_object](#jerry_api_release_object)
- [jerry_api_add_object_field](#jerry_api_add_object_field)
- [jerry_api_delete_object_field](#jerry_api_delete_object_field)
- [jerry_api_get_object_field_value](#jerry_api_get_object_field_value)
- [jerry_api_set_object_field_value](#jerry_api_set_object_field_value)

# jerry_api_add_object_field

**Summary**
Create field (named data property) in an object

**Prototype**

```c
bool
jerry_api_add_object_field (jerry_api_object_t *object_p,
                            const jerry_api_char_t *field_name_p,
                            const jerry_api_value_t *field_value_p,
                            bool is_writable);
```

- `object_p` - object to add field at;
- `field_name_p` - name of the field;
- `field_value_p` - value of the field;
- `is_writable` - flag indicating whether the created field should be writable.
- returned value - true, if field was created successfully, i.e. upon the call:
  - there is no field with same name in the object;
  - the object is extensible.

**Example**

```c
{
  jerry_api_object_t *obj_p = jerry_api_create_object ();

  jerry_api_value_t val;

  ... // initialize val

  // Make new constant field
  jerry_api_add_object_field (obj_p, "some_field_name", &val, false);
}
```


**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_create_object](#jerry_api_create_object)

# jerry_api_delete_object_field

**Summary**
Delete field (property) in the specified object

**Prototype**

```c
bool
jerry_api_delete_object_field (jerry_api_object_t *object_p,
                               const jerry_api_char_t *field_name_p);
```

- `object_p` - object to delete field at;
- `field_name_p` - name of the field.
- returned value - true, if field was deleted successfully, i.e. upon the call:
  - there is field with specified name in the object.

**Example**

```c
{
  jerry_api_object_t *obj_p;
  ... // receive or construct obj_p

  jerry_api_delete_object_field (obj_p, "some_field_name");
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_create_object](#jerry_api_create_object)

# jerry_api_get_object_field_value

**Summary**
Get value of field (property) in the specified object, i.e. perform [[Get]] operation.

**Prototype**

```c
bool
jerry_api_get_object_field_value (jerry_api_object_t *object_p,
                                  const jerry_api_char_t *field_name_p,
                                  jerry_api_value_t *field_value_p);
```

- `object_p` - object;
- `field_name_p` - name of the field;
- `field_value_p` - retrieved field value (output parameter).
- returned value - true, if field value was retrieved successfully, i.e. upon the call:
  - there is field with specified name in the object.

If value was retrieved successfully, it should be freed with [jerry_api_release_object](#jerry_api_release_object) just when it becomes unnecessary.

**Example**

```c
{
  jerry_api_object_t *obj_p;
  ... // receive or construct obj_p

  jerry_api_value_t val;
  bool is_ok = jerry_api_get_object_field_value (obj_p, "some_field_name", &val);
  if (is_ok)
  {
    ... // usage of 'val'

    jerry_api_release_value (&val);
  }
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_create_object](#jerry_api_create_object)


# jerry_api_get_object_field_value_sz

**Summary**

Gets the value of a field in the specified object.
If the value was retrieved successfully, it should be freed with jerry_api_release_value when it becomes unnecessary.

**Prototype**

```c
bool
jerry_api_get_object_field_value_sz (jerry_api_object_t *object_p,
                                     const jerry_api_char_t *field_name_p,
                                     jerry_api_size_t field_name_size,
                                     jerry_api_value_t *field_value_p);
```
- `object_p` - object
- `field_name_p` - name of the field
- `field_name_size` - size of field name in bytes
- `field_value_p` - Output parameter, that gives the value of the field if retrieved
- return value
  - true, if field value was retrieved successfully
  - false, otherwise

**Example**
```c
{
  jerry_init (JERRY_FLAG_EMPTY);

  jerry_api_char_t field_name[] = "field";
  jerry_api_value_t field_value = jerry_api_create_number_value(3.14);

  jerry_api_object_t* object_p = jerry_api_create_object();
  jerry_api_add_object_field(object_p,
                             field_name,
                             (jerry_api_size_t)strlen((char*)field_name),
                             &field_value, true);

  jerry_api_value_t retrieved_field_value = jerry_api_create_undefined_value();
  bool is_get_ok = jerry_api_get_object_field_value_sz(object_p,
                                                       field_name,
                                                       (jerry_api_size_t)strlen((char*)field_name),
                                                       &retrieved_field_value);

  // usage of the retrieved field...

  jerry_api_release_object(object_p);
}
```

**See also**

[jerry_init](#jerry_init)
[jerry_api_create_object](#jerry_api_create_object)
[jerry_api_release_object](#jerry_api_release_object)
[jerry_api_add_object_field](#jerry_api_add_object_field)
[jerry_api_get_object_field_value](#jerry_api_get_object_field_value)
[jerry_api_set_object_field_value](#jerry_api_set_object_field_value)
[jerry_api_set_object_field_value_sz](#jerry_api_set_object_field_value_sz)


# jerry_api_set_object_field_value

**Summary**
Set value of a field (property) in the specified object, i.e. perform [[Put]] operation.

**Prototype**

```c
bool
jerry_api_set_object_field_value (jerry_api_object_t *object_p,
                                  const jerry_api_char_t *field_name_p,
                                  jerry_api_value_t *field_value_p);
```

- `object_p` - object;
- `field_name_p` - name of the field;
- `field_value_p` - field value to set.
- returned value - true, if field value was set successfully, i.e. upon the call:
  - field value is writable.

**Example**

```c
{
  jerry_api_object_t *obj_p;
  jerry_api_value_t val;

  ... // receive or construct obj_p and val

  bool is_ok = jerry_api_set_object_field_value (obj_p, "some_field_name", &val);
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_create_object](#jerry_api_create_object)

# jerry_api_get_object_native_handle

**Summary**

Get native handle, previously associated with specified object.

**Prototype**

```c
bool
jerry_api_get_object_native_handle (jerry_api_object_t *object_p,
                                    uintptr_t *out_handle_p);
```

- `object_p` - object to get handle from;
- `out_handle_p` - handle value (output parameter);
- returned value - true, if there is handle associated with the object.

**Example**

```c
{
  jerry_api_object_t *obj_p;
  uintptr_t handle_set;

  ... // receive or construct obj_p and handle_set value

  jerry_api_set_object_native_handle (obj_p, handle_set, NULL);

  ...

  uintptr_t handle_get;
  bool is_there_associated_handle = jerry_api_get_object_native_handle (obj_p,
                                                                        &handle_get);
}
```

**See also**

- [jerry_api_create_object](#jerry_api_create_object)
- [jerry_api_set_object_native_handle](#jerry_api_set_object_native_handle)

# jerry_api_set_object_native_handle

**Summary**

Set native handle and, optionally, "free" callback for the specified object.

If native handle or "free" callback were already set for the object, corresponding value is updated.

**Prototype**

```c
void
jerry_api_set_object_native_handle (jerry_api_object_t *object_p,
                                    uintptr_t handle,
                                    jerry_object_free_callback_t freecb_p);
```

- `object_p` - object to set handle in;
- `handle` - handle value;
- `freecb_p` - pointer to "free" callback or NULL (if not NULL the callback would be called upon GC of the object).

**Example**

```c
{
  jerry_api_object_t *obj_p;
  uintptr_t handle_set;

  ... // receive or construct obj_p and handle_set value

  jerry_api_set_object_native_handle (obj_p, handle_set, NULL);

  ...

  uintptr_t handle_get;
  bool is_there_associated_handle = jerry_api_get_object_native_handle (obj_p,
                                                                        &handle_get);
}
```

**See also**

- [jerry_api_create_object](#jerry_api_create_object)
- [jerry_api_get_object_native_handle](#jerry_api_get_object_native_handle)

# jerry_api_is_function

**Summary**
Check whether the specified object is a function object.

**Prototype**

```c
bool
jerry_api_is_function (const jerry_api_object_t *object_p);
```

- `object_p` - object to check;
- returned value - just boolean, indicating whether the specified object can be called as function.

**Example**

```c
{
  jerry_api_value_t val;

  ... // receiving val

  if (val.type == JERRY_API_DATA_TYPE_OBJECT)
  {
    if (jerry_api_is_function (val.u.v_object))
    {
      // the object is function object
    }
  }
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_is_constructor](#jerry_api_is_constructor)
- [jerry_api_call_function](#jerry_api_call_function)

# jerry_api_is_constructor

**Summary**
Check whether the specified object is a constructor function object.

**Prototype**

```c
bool
jerry_api_is_constructor (const jerry_api_object_t *object_p);
```

- `object_p` - object to check;
- returned value - just boolean, indicating whether the specified object can be called as constructor.

**Example**

```c
{
  jerry_api_value_t val;

  ... // receiving val

  if (val.type == JERRY_API_DATA_TYPE_OBJECT)
  {
    if (jerry_api_is_constructor (val.u.v_object))
    {
      // the object is constructor function object
    }
  }
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_is_function](#jerry_api_is_function)
- [jerry_api_construct_object](#jerry_api_construct_object)

# jerry_api_call_function

**Summary**
Call function object.

**Prototype**

```c
bool
jerry_api_call_function (jerry_api_object_t *function_object_p,
                         jerry_api_object_t *this_arg_p,
                         jerry_api_value_t *retval_p,
                         const jerry_api_value_t args_p[],
                         uint16_t args_count);
```

- `function_object_p` - the function object to call;
- `this_arg_p` - object to use as 'this' during the invocation, or NULL - to set the Global object as 'this';
- `retval_p` - function's return value (output parameter);
- `args_p`, `args_count` - array of arguments and number of them;
- returned value - true, if call was performed successfully, i.e.:
  - specified object is a function object (see also jerry_api_is_function);
  - no unhandled exceptions were thrown in connection with the call.

 If call was performed successfully, returned value should be freed with [jerry_api_release_object](#jerry_api_release_object) just when it becomes unnecessary.

**Example**

```c
{
  jerry_api_value_t val;

  ... // receiving val

  if (val.type == JERRY_API_DATA_TYPE_OBJECT)
  {
    if (jerry_api_is_function (val.u.v_object))
    {
      jerry_api_value_t ret_val;

      bool is_ok = jerry_api_call_function (val.u.v_object,
                                            NULL,
                                            &ret_val,
                                            NULL, 0);

      if (is_ok)
      {
        ... // handle return value

        jerry_api_release_value (&ret_val);
      }
    }
  }
}
```

**See also**

- [jerry_api_is_function](#jerry_api_is_function)
- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_create_external_function](#jerry_api_create_external_function)

# jerry_api_construct_object

**Summary**
Construct object invoking specified function object as constructor.

**Prototype**

```c
bool
jerry_api_construct_object (jerry_api_object_t *function_object_p,
                            jerry_api_value_t *retval_p,
                            const jerry_api_value_t args_p[],
                            uint16_t args_count);
```

- `function_object_p` - the function object to invoke;
- `retval_p` - return value of function invoked as constructor, i.e. like with 'new' operator (output parameter);
- `args_p`, `args_count` - array of arguments and number of them;
- returned value - true, if call was performed successfully, i.e.:
  - specified object is a constructor function object;
  - no unhandled exceptions were thrown in connection with the call.

If call was performed successfully, returned value should be freed with [jerry_api_release_object](#jerry_api_release_object) just when it becomes unnecessary.

**Example**

```c
{
  jerry_api_value_t val;

  ... // receiving val

  if (val.type == JERRY_API_DATA_TYPE_OBJECT)
  {
    if (jerry_api_is_constructor (val.u.v_object))
    {
      jerry_api_value_t ret_val;

      bool is_ok = jerry_api_construct_object (val.u.v_object,
                                               &ret_val,
                                               NULL, 0);

      if (is_ok)
      {
        ... // handle return value

        jerry_api_release_value (&ret_val);
      }
    }
  }
}
```

**See also**

 - [jerry_api_is_constructor](#jerry_api_is_constructor)
 - [jerry_api_value_t](#jerry_api_value_t)

# jerry_external_handler_t

**Summary**

The data type represents pointer to call handler of a native function object.

**Structure**

```c
typedef bool (* jerry_external_handler_t) (const jerry_api_object_t *function_obj_p,
                                           const jerry_api_value_t *this_p,
                                           jerry_api_value_t *ret_val_p,
                                           const jerry_api_value_t args_p[],
                                           const uint16_t args_count);
```

**See also**

- [jerry_api_create_external_function](#jerry_api_create_external_function)

# jerry_api_create_external_function

**Summary**
Create an external function object.

**Prototype**

```c
jerry_api_object_t *
jerry_api_create_external_function (jerry_external_handler_t handler_p);
```

- `handler_p` - pointer to native handler of the function object;
- returned value - pointer to constructed external function object.

Received pointer should be released with [jerry_api_release_object](#jerry_api_release_object), just when the value becomes unnecessary.

**Example**

```c
static bool
handler (const jerry_api_object_t *function_obj_p,
         const jerry_api_value_t *this_p,
         jerry_api_value_t *ret_val_p,
         const jerry_api_value_t args_p[],
         const uint16_t args_cnt)
{
  printf ("native handler called!\n");

  ret_val_p->type = JERRY_API_DATA_TYPE_BOOLEAN;
  ret_val_p->u.v_bool = true;
}

{
  jerry_api_object_t *obj_p = jerry_api_create_external_function (handler);
  jerry_api_object_t *glob_obj_p = jerry_api_get_global ();

  jerry_api_value_t val;
  val.type = JERRY_API_DATA_TYPE_OBJECT;
  val.u.v_object = obj_p;

  // after this, script can invoke the native handler through "handler_field (1, 2, 3);"
  jerry_api_set_object_field_value (glob_obj_p, "handler_field", &val);

  jerry_api_release_object (glob_obj_p);
  jerry_api_release_object (obj_p);
}
```

**See also**

- [jerry_external_handler_t](#jerry_external_handler_t)
- [jerry_api_is_function](#jerry_api_is_function)
- [jerry_api_call_function](#jerry_api_call_function)
- [jerry_api_release_object](#jerry_api_release_object)

# jerry_api_create_array_object

**Summary**
Create new JavaScript array object.

Upon the JavaScript array object becomes unused, all pointers to it should be released using [jerry_api_release_object](#jerry_api_release_object).

**Prototype**

```c
jerry_api_object_t *
jerry_api_create_array_object (jerry_api_size_t array_size);
```

 - `array_size` - size of array;
 - returned value is pointer to the created array object.

 **Example**

```c
{
    jerry_api_object_t *array_object_p = jerry_api_create_array_object (10);

    ...

    jerry_api_release_object (array_object_p);
}
```

**See also**

- [jerry_api_acquire_object](#jerry_api_acquire_object)
- [jerry_api_release_object](#jerry_api_release_object)
- [jerry_api_set_array_index_value](#jerry_api_set_array_index_value)
- [jerry_api_get_array_index_value](#jerry_api_get_array_index_value)
- [jerry_api_add_object_field](#jerry_api_add_object_field)
- [jerry_api_delete_object_field](#jerry_api_delete_object_field)
- [jerry_api_get_object_field_value](#jerry_api_get_object_field_value)
- [jerry_api_set_object_field_value](#jerry_api_set_object_field_value)
- [jerry_api_get_object_native_handle](#jerry_api_get_object_native_handle)
- [jerry_api_set_object_native_handle](#jerry_api_set_object_native_handle)

# jerry_api_set_array_index_value

**Summary**
Set value of an indexed element in the specified array object.

**Prototype**

```c
bool
jerry_api_set_array_index_value (jerry_api_object_t *array_object_p,
                                 jerry_api_length_t index,
                                 jerry_api_value_t *value_p);
```

- `array_object_p` - pointer to the array object;
- `index` - index of the array element;
- `value_p` - indexed value to set;
- returned value - true, if value was set successfully.

**Example**

```c
{
    jerry_api_object_t *array_object_p = jerry_api_create_array_object (10);
    jerry_api_value_t val;

    ... // receive or construct val

    jerry_api_set_array_index_value (array_object_p, 5, &val);

    jerry_api_release_object (array_object_p);
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_create_array_object](#jerry_api_create_array_object)

# jerry_api_get_array_index_value

**Summary**
Get value of an indexed element in the specified array object.

**Prototype**

```c
bool
jerry_api_get_array_index_value (jerry_api_object_t *array_object_p,
                                 jerry_api_length_t index,
                                 jerry_api_value_t *value_p);
```

- `array_object_p` - pointer to the array object;
- `index` - index of the array element;
- `value_p` - retrieved indexed value (output parameter);
- returned value - true, if value was retrieved successfully.

**Example**

```c
{
    jerry_api_object_t *array_object_p;
    ... // receive or construct array_object_p

    jerry_api_value_t val;
    bool is_ok = jerry_api_get_array_index_value (array_object_p, 5, &val);
    if (is_ok)
    {
        ... // usage of 'val'
    }
}
```

**See also**

- [jerry_api_value_t](#jerry_api_value_t)
- [jerry_api_create_array_object](#jerry_api_create_array_object)


# jerry_api_create_error

**Summary**
Create new JavaScript error object.
it should be throwed inside of handle attached to external function object.

**Prototype**

```c
jerry_api_object_t *
jerry_api_create_error (jerry_api_error_t error_type,
                        const jerry_api_char_t *message_p);
```

- `error_type` - error type of object;
- `message_p` - human-readable description of the error;
- returned value is pointer to the created error object.

**Example**

```c
static bool
handler (const jerry_api_object_t *function_obj_p,
         const jerry_api_value_t *this_p,
         jerry_api_value_t *ret_val_p,
         const jerry_api_value_t args_p[],
         const uint16_t args_cnt)
{
  jerry_api_object_t *error_p = jerry_api_create_error (JERRY_API_ERROR_TYPE,
                                                        (jerry_api_char_t * ) "error");

  jerry_api_acquire_object (error_p);
  ret_val_p->type = JERRY_API_DATA_TYPE_OBJECT;
  ret_val_p->u.v_object = error_p;

  jerry_api_release_object (error_p);

  return false;
}

{
  jerry_api_object_t *throw_obj_p = jerry_api_create_external_function (handler);
  jerry_api_object_t *glob_obj_p = jerry_api_get_global ();

  jerry_api_value_t val;
  val.type = JERRY_API_DATA_TYPE_OBJECT;
  val.u.v_object = throw_obj_p;

  // after this, script can invoke the native handler through "error_func ();"
  // and "error_func" throw a error on called
  jerry_api_set_object_field_value (glob_obj_p, "error_func", &val);

  jerry_api_release_object (glob_obj_p);
  jerry_api_release_object (throw_obj_p);
}
```

**See also**
- [jerry_external_handler_t](#jerry_external_handler_t)
- [jerry_api_is_function](#jerry_api_is_function)
- [jerry_api_call_function](#jerry_api_call_function)
- [jerry_api_release_object](#jerry_api_release_object)
- [jerry_api_create_external_function](#jerry_api_create_external_function)





# jerry_register_external_magic_strings

**Summary**
Registers an external magic string array.

**Prototype**
```c
void
jerry_register_external_magic_strings  (const jerry_api_char_ptr_t *ex_str_items,
                                        uint32_t  count,
                                        const jerry_api_length_t *  str_lengths);
```

- `ex_str_items` - character arrays, representing external magic strings' contents
- `count number` - of the strings
- `str_lengths` - lengths of the strings

**Example**
```c
{
  jerry_init (JERRY_FLAG_EMPTY);

  const jerry_api_char_ptr_t magic_string_items[] = {
                                                      (const jerry_api_char_ptr_t)"magicstring1",
                                                      (const jerry_api_char_ptr_t)"magicstring2",
                                                      (const jerry_api_char_ptr_t)"magicstring3"
                                                    };
  uint32_t num_magic_string_items = (uint32_t) (sizeof (magic_string_items) / sizeof (jerry_api_char_ptr_t));
  const jerry_api_length_t magic_string_lengths[] = {
                                                      (jerry_api_length_t)strlen(magic_string_items[0]),
                                                      (jerry_api_length_t)strlen(magic_string_items[1]),
                                                      (jerry_api_length_t)strlen(magic_string_items[2])
                                                    };
  jerry_register_external_magic_strings (magic_string_items,
                                         num_magic_string_items,
                                         magic_string_lengths);
}
```

**See also**
- [jerry_init](#jerry_init)
