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

# jerry_init

## Summary

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

## Prototype

{% highlight cpp %}
void jerry_init (jerry_flag_t flags);
{% endhighlight %}

`flags` - combination of various engine configuration flags:

- `JERRY_FLAG_MEM_STATS` - dump memory statistics;
- `JERRY_FLAG_ENABLE_LOG` - enable logging;
- `JERRY_FLAG_SHOW_OPCODES` - print compiled byte-code;
- `JERRY_FLAG_EMPTY` - no flags, just initialize in default configuration.

## See also
- [jerry_cleanup](/API#jerry_cleanup)

## Example

{% highlight cpp %}
{
  jerry_init (JERRY_FLAG_ENABLE_LOG);

  // ...

  jerry_cleanup ();
}
{% endhighlight %}

# jerry_cleanup

## Summary

Finish JavaScript engine execution, freeing memory and JavaScript values.

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

## Prototype

{% highlight cpp %}
void jerry_cleanup (void)
{% endhighlight %}

## See also
- [jerry_init](/API#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

{% highlight cpp %}
bool jerry_parse (const char* source_p, size_t source_size)
{% endhighlight %}
- `source_p` - string, containing source code to parse;
- `source_size` - size of the string, in bytes.

## See also
- [jerry_run](/API#jerry_run)

## Example
{% highlight cpp %}
 {
   jerry_init (JERRY_FLAG_ENABLE_LOG);

   char script [] = "print ('Hello, World!');";
   jerry_parse (script, strlen (script));

   jerry_run ();

   jerry_cleanup ();
 }
{% endhighlight %}

# jerry_run

## Summary
Run Global scope's code.

The code should be previously registered through `jerry_parse`.

## Prototype

{% highlight cpp %}
jerry_completion_code_t jerry_run (void)
{% endhighlight %}

Returned completion code indicates whether run performed successfully (`JERRY_COMPLETION_CODE_OK`), or an unhandled JavaScript exception occurred (`JERRY_COMPLETION_CODE_UNHANDLED_EXCEPTION`).

## See also
- [jerry_parse](/API#jerry_parse)

## Example

{% highlight cpp %}
{
  jerry_init (JERRY_FLAG_ENABLE_LOG);

  char script [] = "print ('Hello, World!');";
  jerry_parse (script, strlen (script));

  jerry_run ();

  jerry_cleanup ();
}
{% endhighlight %}

# jerry_api_value_t

## Summary
The data type represents any JavaScript value that can be sent to / 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_UNDEFINED` - JavaScript undefined;
- `JERRY_API_DATA_TYPE_NULL` - JavaScript null;
- `JERRY_API_DATA_TYPE_BOOLEAN` - boolean;
- `JERRY_API_DATA_TYPE_FLOAT64` - number;
- `JERRY_API_DATA_TYPE_STRING` - string;
- `JERRY_API_DATA_TYPE_OBJECT` - reference to JavaScript object.

## Structure

{% highlight cpp %}
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;

    union
    {
      jerry_api_string_t *v_string;
      jerry_api_object_t *v_object;
    };
  };
} jerry_api_value_t;
{% endhighlight %}

## See also
- [jerry_api_string_t](/API#jerry_api_string_t)
- [jerry_api_object_t](/API#jerry_api_object_t)
- [jerry_api_eval](/API#jerry_api_eval)
- [jerry_api_call_function](/API#jerry_api_call_function)
- [jerry_api_construct_object](/API#jerry_api_construct_object)


# jerry_api_eval

## Summary
Perform JavaScript `eval`.

## Prototype

{% highlight cpp %}
jerry_completion_code_t
jerry_api_eval (const char *source_p,
                size_t source_size,
                bool is_direct,
                bool is_strict,
                jerry_api_value_t *retval_p);
{% endhighlight %}

- `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).

## See also
- [jerry_api_create_external_function](/API#jerry_api_create_external_function)
- [jerry_api_value_t](/API#jerry_api_value_t)

## Example
{% highlight cpp %}
{
  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);
}
{% endhighlight %}

# 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](/API#jerry_api_release_string).

## Prototype

{% highlight cpp %}
jerry_api_string_t* jerry_api_create_string (const char *v)
{% endhighlight %}

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


## See also
- [jerry_api_acquire_string](/API#jerry_api_acquire_string)
- [jerry_api_release_string](/API#jerry_api_release_string)

## Example
{% highlight cpp %}
{
  jerry_api_string_t *string_p = jerry_api_create_string ("abc");

  ...

  jerry_api_release_string (string_p);
}
{% endhighlight %}

# 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](/API#jerry_api_release_string).

## Prototype

{% highlight cpp %}
jerry_api_string_t* jerry_api_acquire_string (jerry_api_string_t *string_p)
{% endhighlight %}

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

## See also
- [jerry_api_release_string](/API#jerry_api_release_string)
- [jerry_api_create_string](/API#jerry_api_create_string)

## Example
{% highlight cpp %}
{
  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);
}
{% endhighlight %}

# jerry_api_release_string

## Summary
Release specified pointer to the string.

## Prototype

{% highlight js %}
void jerry_api_release_string (jerry_api_string_t *string_p)
{% endhighlight %}

## See also
- [jerry_api_acquire_string](/API#jerry_api_acquire_string)
- [jerry_api_create_string](/API#jerry_api_create_string)

## Example
{% highlight cpp %}
{
  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);
}
{% endhighlight %}

# 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](/API#jerry_api_release_object).

## Prototype

{% highlight cpp %}
jerry_api_object_t* jerry_api_create_object (const char *v)
{% endhighlight %}

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


## See also
- [jerry_api_acquire_object](/API#jerry_api_acquire_object)
- [jerry_api_release_object](/API#jerry_api_release_object)

## Example
{% highlight cpp %}
{
  jerry_api_object_t *object_p = jerry_api_create_object ("abc");

  ...

  jerry_api_release_object (object_p);
}
{% endhighlight %}

# 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](/API#jerry_api_release_object).

## Prototype

{% highlight cpp %}
jerry_api_object_t* jerry_api_acquire_object (jerry_api_object_t *object_p)
{% endhighlight %}

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

## See also
- [jerry_api_release_object](/API#jerry_api_release_object)
- [jerry_api_create_object](/API#jerry_api_create_object)

## Example
{% highlight cpp %}
{
  jerry_api_object_t *obj_ptr1_p = jerry_api_create_object ("abc");
  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);
}
{% endhighlight %}

# jerry_api_release_object

## Summary
Release specified pointer to the object.

## Prototype

{% highlight cpp %}
void jerry_api_release_object (jerry_api_object_t *object_p)
{% endhighlight %}

## See also
- [jerry_api_acquire_object](/API#jerry_api_acquire_object)
- [jerry_api_create_object](/API#jerry_api_create_object)

## Example
{% highlight cpp %}
{
  jerry_api_object_t *obj_ptr1_p = jerry_api_create_object ("abc");
  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);
}
{% endhighlight %}

# jerry_api_is_function

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

## Prototype

{% highlight cpp %}
bool jerry_api_is_function (const jerry_api_object_t* object_p)
{% endhighlight %}

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

## See also
- [jerry_api_value_t](/API#jerry_api_value_t)
- [jerry_api_is_constructor](/API#jerry_api_is_constructor)
- [jerry_api_call_function](/API#jerry_api_call_function)

## Example
{% highlight cpp %}
{
  jerry_api_value_t val;

  ... // receiving val

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

# jerry_api_is_constructor

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

## Prototype

{% highlight cpp %}
bool jerry_api_is_constructor (const jerry_api_object_t* object_p)
{% endhighlight %}

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

## See also
- [jerry_api_value_t](/API#jerry_api_value_t)
- [jerry_api_is_function](/API#jerry_api_is_function)
- [jerry_api_construct_object](/API#jerry_api_construct_object)

## Example
{% highlight cpp %}
{
  jerry_api_value_t val;

  ... // receiving val

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

# jerry_api_call_function

## Summary
Call function object.

## Prototype

{% highlight cpp %}
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)
{% endhighlight %}

- `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_value](/API#jerry_api_release_value) just when it becomes unnecessary.

## See also
- [jerry_api_is_function](/API#jerry_api_is_function)
- [jerry_api_value_t](/API#jerry_api_value_t)

## Example
{% highlight cpp %}
{
  jerry_api_value_t val;

  ... // receiving val

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

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

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

        jerry_api_release_value (&ret_val);
      }
    }
  }
}
{% endhighlight %}