examples: add javascript example

examples/javascript/Makefile

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+# application name
+APPLICATION = riot_javascript
+
+# default BOARD environment
+BOARD ?= native
+
+BOARD_INSUFFICIENT_MEMORY := airfy-beacon calliope-mini cc2650stk maple-mini \
+                             microbit nrf51dongle nrf6310 nucleo-f030 nucleo-f070 \
+                             nucleo-f072 nucleo-f103 nucleo-f302 nucleo-f334 nucleo-f410 \
+                             nucleo-l053 nucleo-l073 nucleo32-f031 nucleo32-f042 \
+                             nucleo32-f303 nucleo32-l031 opencm904 pca10000 \
+                             pca10005 spark-core stm32f0discovery weio yunjia-nrf51822 \
+
+BOARD_BLACKLIST := arduino-duemilanove arduino-mega2560 arduino-uno chronos \
+                   msb-430 msb-430h qemu-i386 telosb waspmote-pro wsn430-v1_3b \
+                   wsn430-v1_4 z1
+
+# Comment this out to disable code in RIOT that does safety checking
+# which is not needed in a production environment but helps in the
+# development process:
+CFLAGS += -DDEVELHELP
+
+# Set stack size to something (conservatively) enormous
+CFLAGS += -DTHREAD_STACKSIZE_MAIN=9092
+
+# Add the shell and some shell commands
+USEMODULE += shell
+USEMODULE += shell_commands
+
+# Add the package for Jerryscript
+USEPKG += jerryscript
+
+include $(CURDIR)/../../Makefile.include

examples/javascript/README.md

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+### About
+
+This example enables to execute arbitrary Javascript directly from the command line on the RIOT shell.
+
+### Acknowledgement
+This example is based on [Jerryscript](https://github.com/jerryscript-project/jerryscript) which does all the heavy lifting, providing full ECMAScript 5.1 profile on your IoT device (kudos guys!).
+
+### Caveats
+
+- On your local board: best used with a serial communication program such [minicom](https://help.ubuntu.com/community/Minicom) instead of PyTerm (see why below).
+
+- On a testbed: you can try it on [IoT-lab](https://www.iot-lab.info). Tested and works so far on [IoT-lab M3](https://www.iot-lab.info/hardware/m3/), upload and flash the .elf, ssh into the node, and script away!
+
+- Except in the `print` instruction in your script, you have to replace single brackets `'` with `\'`.
+
+- Expect some issues with PyTerm which interprets by default the first `;` as the end of the script command. Furthermore, if the script is long, PyTerm seems to get confused (hence the recommended use of minicom). To start playing with PyTerm, first edit `;` line 256 of RIOT/dist/tools/pyterm/pyterm
+
+### How to build
+
+Type `make flash`. Then use your preferred serial communication tool to land in the RIOT shell.
+Note: you may have to type `reboot` or to press `RESET` on the board (after the flash).
+
+### Running the example
+
+In the RIOT shell, `help` will provide the list of available commands.
+
+The `script` command will run the test script code that you input in the command line.
+Some examples of scripts you can try:
+```
+script print ('hello');
+```
+```
+script var x = Math.sqrt (64); var txt = \'\'; while (x>1) { txt += --x + \'\\n\';} print (txt);
+```
+```
+script var person = { fname:\'John\', lname:\'Doe\', age:25 }; var text = \'\'; var x; for (x in person) { text += person[x] + \'\\n\'; } print (text);
+```
+
+Remark: outside of the print command, you may have to replace single brackets ' with \'.

examples/javascript/main.c

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+/*
+ * Copyright (C) 2017 Inria
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     examples
+ * @{
+ *
+ * @file
+ * @brief       Showing an example of scripting (javascript) from command line
+ *
+ * @author      Emmanuel Baccelli <emmanuel.baccelli@inria.fr>
+ *
+ * @}
+ */
+
+#include <string.h>
+#include "shell.h"
+#include "jerryscript.h"
+
+int shell_script(int argc, char **argv)
+{
+    if (argc < 2) {
+        puts("Usage: script <your script here!> \n"
+        "For example, try: \n"
+        "script var txt = \\'\\'; txt += Math.PI; print (\\'Pi=\\'+txt); \n"
+        "Note: you need to substitute usual quotes with \\' \n");
+        return -1;
+    }
+
+    jerry_char_t script[(2 * SHELL_DEFAULT_BUFSIZE + 1)];
+    *script = '\0';
+    for(int i = 1; i < argc; i++) {
+        if (i>1) {
+            strcat((char *)script, " ");
+        }
+        strcat((char *)script, argv[i]);
+    }
+
+    size_t script_size = strlen((char *) script);
+    printf("Executing script: [%s]\n\n", script);
+    bool ret_value = jerry_run_simple(script, script_size, JERRY_INIT_EMPTY);
+
+    return (ret_value != 0);
+}
+
+const shell_command_t shell_commands[] = {
+    { "script", "Shell scripting ", shell_script },
+    { NULL, NULL, NULL }
+};
+
+int main(void)
+{
+    printf("You are running RIOT on a(n) %s board.\n", RIOT_BOARD);
+    printf("This board features a(n) %s MCU.\n", RIOT_MCU);
+
+    /* start the shell */
+    char line_buf[2 * SHELL_DEFAULT_BUFSIZE];
+    /* for longer script support shell buffer should be bigger */
+    shell_run(shell_commands, line_buf, sizeof(line_buf));
+
+    return 0;
+}