Add new API examples
JerryScript-DCO-1.0-Signed-off-by: László Langó llango.u-szeged@partner.samsung.com
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László Langó
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@@ -369,7 +369,229 @@ main (int argc, char * argv[])
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The application inputs commands and evaluates them, one after another.
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## Step 6. Creating JS object in global context
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In this example we demonstrate how to use native function and structures in JavaScript.
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```c
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#include <string.h>
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#include "jerry.h"
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struct my_struct
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{
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const char *msg;
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} my_struct;
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/**
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* Get a string from a native object
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*/
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static bool
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get_msg_handler (const jerry_api_object_t *function_obj_p, /**< function object */
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const jerry_api_value_t *this_p, /**< this arg */
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jerry_api_value_t *ret_val_p, /**< return argument */
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const jerry_api_value_t *args_p, /**< function arguments */
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const jerry_api_length_t args_cnt) /**< number of function arguments */
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{
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jerry_api_string_t *msg_str_p = jerry_api_create_string ((const jerry_api_char_t *) my_struct.msg);
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*ret_val_p = jerry_api_create_string_value (msg_str_p);
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return true;
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} /* get_msg_handler */
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int
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main (int argc, char * argv[])
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{
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jerry_completion_code_t status = JERRY_COMPLETION_CODE_OK;
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/* Initialize engine */
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jerry_init (JERRY_FLAG_EMPTY);
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/* Do something with the native object */
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my_struct.msg = "Hello World";
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/* Create an empty JS object */
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jerry_api_object_t *object_p = jerry_api_create_object ();
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/* Create a JS function object and wrap into a jerry value */
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jerry_api_value_t object_value;
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object_value.type = JERRY_API_DATA_TYPE_OBJECT;
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object_value.u.v_object = jerry_api_create_external_function (get_msg_handler);
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/* Set the native function as a property of the empty JS object */
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jerry_api_set_object_field_value (object_p,
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(const jerry_api_char_t *) "myFunc",
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&object_value);
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jerry_api_release_value (&object_value);
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/* Wrap the JS object (not empty anymore) into a jerry api value */
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object_value.type = JERRY_API_DATA_TYPE_OBJECT;
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object_value.u.v_object = object_p;
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jerry_api_object_t *global_obj_p = jerry_api_get_global ();
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/* Add the JS object to the global context */
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jerry_api_set_object_field_value (global_obj_p,
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(const jerry_api_char_t *) "MyObject",
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&object_value);
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jerry_api_release_value (&object_value);
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jerry_api_release_object (global_obj_p);
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/* Now we have a "builtin" object called MyObject with a function called myFunc()
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*
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* Equivalent JS code:
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* var MyObject = { myFunc : function () { return "some string value"; } }
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*/
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const jerry_api_char_t script[] = " \
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var str = MyObject.myFunc (); \
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print (str); \
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";
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size_t script_size = strlen ((const char *) script);
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jerry_api_value_t eval_ret;
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/* Evaluate script */
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status = jerry_api_eval (script,
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script_size,
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false,
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false,
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&eval_ret);
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/* Free JavaScript value, returned by eval */
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jerry_api_release_value (&eval_ret);
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/* Cleanup engine */
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jerry_cleanup ();
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return (int) status;
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}
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```
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The application will generate the following output:
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```bash
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Hello World
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```
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## Step 7. Extending JS Objects with native functions
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Here we create a JS Object with `jerry_api_eval`, then extend it with a native function. This function shows how to get a property value from the object and how to manipulate it.
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```c
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#include <string.h>
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#include "jerry.h"
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/**
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* Add param to 'this.x'
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*/
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static bool
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add_handler (const jerry_api_object_t *function_obj_p, /**< function object */
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const jerry_api_value_t *this_p, /**< this arg */
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jerry_api_value_t *ret_val_p, /**< return argument */
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const jerry_api_value_t *args_p, /**< function arguments */
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const jerry_api_length_t args_cnt) /**< number of function arguments */
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{
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jerry_api_value_t x_val;
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/* Get 'this.x' */
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if (jerry_api_get_object_field_value (jerry_api_get_object_value (this_p),
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(const jerry_api_char_t *) "x",
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&x_val))
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{
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/* Convert Jerry API values to double */
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double x = jerry_api_get_number_value (&x_val);
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double d = jerry_api_get_number_value (args_p);
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/* Add the parameter to 'x' */
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jerry_api_value_t res_val = jerry_api_create_number_value (x + d);
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/* Set the new value of 'this.x' */
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jerry_api_set_object_field_value (jerry_api_get_object_value (this_p),
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(const jerry_api_char_t *) "x",
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&res_val);
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}
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return true;
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} /* add_handler */
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int
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main (int argc, char * argv[])
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{
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jerry_completion_code_t status = JERRY_COMPLETION_CODE_OK;
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/* Initialize engine */
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jerry_init (JERRY_FLAG_EMPTY);
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/* Create a JS object */
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const jerry_api_char_t my_js_object[] = " \
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MyObject = \
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{ x : 12, \
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y : 'Value of x is ', \
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foo: function () \
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{ \
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return this.y + this.x; \
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} \
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} \
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";
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jerry_api_value_t my_js_obj_val;
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/* Evaluate script */
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status = jerry_api_eval (my_js_object,
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strlen ((const char *) my_js_object),
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false,
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false,
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&my_js_obj_val);
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jerry_api_object_t *object_p = jerry_api_get_object_value (&my_js_obj_val);
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/* Create a JS function object and wrap into a jerry value */
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jerry_api_value_t object_value;
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object_value.type = JERRY_API_DATA_TYPE_OBJECT;
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object_value.u.v_object = jerry_api_create_external_function (add_handler);
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/* Set the native function as a property of previously created MyObject */
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jerry_api_set_object_field_value (object_p,
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(const jerry_api_char_t *) "add2x",
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&object_value);
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jerry_api_release_value (&object_value);
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/* Free JavaScript value, returned by eval (my_js_object) */
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jerry_api_release_value (&my_js_obj_val);
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const jerry_api_char_t script[] = " \
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var str = MyObject.foo (); \
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print (str); \
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MyObject.add2x (5); \
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print (MyObject.foo ()); \
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";
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size_t script_size = strlen ((const char *) script);
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jerry_api_value_t eval_ret;
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/* Evaluate script */
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status = jerry_api_eval (script,
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script_size,
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false,
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false,
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&eval_ret);
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/* Free JavaScript value, returned by eval */
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jerry_api_release_value (&eval_ret);
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/* Cleanup engine */
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jerry_cleanup ();
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return (int) status;
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}
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```
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The application will generate the following output:
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```bash
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Value of x is 12
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Value of x is 17
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```
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## Further steps
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For further API description, please look at [Embedding API](/API).
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For further API description, please look at [API Reference](/docs/API-REFERENCE.md).
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