jerryscript/05.dev-guide.md

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page	Development	/dev-guide/

Embedding

The JerryScript Engine can be embedded into any application, providing way to run JavaScript in large range of environments - from desktops to low-memory microcontrollers.

How to execute simple JavaScript file from your application

#include <string.h>
#include "jerry.h"

int
main (int argc, char * argv[]) {
  char script [] = "print ('Hello, World!');";

  jerry_init (JERRY_FLAG_EMPTY);

  jerry_parse (script, strlen (script));
  jerry_run ();

  jerry_cleanup ();
}

The described application will generate the following output:

Hello, World!

Simple JavaScript shell

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "jerry.h"

static void
print_value (const jerry_api_value_t * value_p);

int
main (int argc, char * argv[]) {
  jerry_init (JERRY_FLAG_EMPTY);

  char cmd [256];
  while (true) {
    printf ("> ");

    if (fgets (cmd, sizeof (cmd), stdin) == NULL
        || strcmp (cmd, "quit\n") == 0) {
      break;
    }

    jerry_api_value_t ret_val;

    jerry_completion_code_t status = jerry_api_eval (cmd, strlen (cmd),
                                                     false, false,
                                                     &ret_val);

    if (status == JERRY_COMPLETION_CODE_OK) {
      // 'eval' completed successfully
      print_value (&ret_val);
      jerry_api_release_value (&ret_val);
    } else {
      // evaluated JS code thrown an exception
      // and didn't handle it with try-catch-finally
      printf ("Unhandled JS exception occured\n");
    }

    printf ("\n");
    fflush (stdout);
  }

  jerry_cleanup ();

  return 0;
}

static void
print_value (const jerry_api_value_t * value_p)
{
  switch (value_p->type)
  {
    case JERRY_API_DATA_TYPE_UNDEFINED:
      printf ("undefined");
      break;
    case JERRY_API_DATA_TYPE_NULL:
      printf ("null");
      break;
    case JERRY_API_DATA_TYPE_BOOLEAN:
      if (value_p->v_bool)
        printf ("true");
      else
        printf ("false");
      break;
    case JERRY_API_DATA_TYPE_FLOAT64:
      printf ("%lf", value_p->v_float64);
      break;
    case JERRY_API_DATA_TYPE_STRING:
    {
      ssize_t neg_req_sz, sz;
      // determining required buffer size
      neg_req_sz = jerry_api_string_to_char_buffer (value_p->v_string,
                                                    NULL,
                                                    0);
      assert (neg_req_sz < 0);
      char * str_buf_p = (char*) malloc (-neg_req_sz);
      sz = jerry_api_string_to_char_buffer (value_p->v_string,
                                            str_buf_p,
                                            -neg_req_sz);
      assert (sz == -neg_req_sz);

      printf ("%s", str_buf_p);

      free (str_buf_p);
      break;
    }
    case JERRY_API_DATA_TYPE_OBJECT:
      printf ("[JS object]");
      break;
  }

  printf ("\n");
}