ESP8266-Arduino-JavaScript

JavaScript scripting engine Arduino IDE Library for ESP8266

ESP8266-Arduino-JavaScript is a Arduino IDE Library to implement a JavaScript engine for ESP8266 microcontroller.

Library Install

• Download the latest github release zip file ESP8266-Arduino-JavaScript-0.0.12
• In the Arduino IDE, navigate to Sketch > Include Library > Add .ZIP Library. At the top of the drop down list, select the option to "Add .ZIP Library''.
• You will be prompted to select the library you would like to add. Navigate to the .zip file's location and open it.
• Load the demo sketch using the Arduino IDE menu (File->Examples->ESP8266-Arduino-JavaScript->blink)
• Build and Upload.

Features

• Clean ISO C, ISO C++. Builds on old (VC98) and modern compilers, from 8-bit (e.g. Arduino mini) to 64-bit systems
• No dependencies
• Implements a restricted subset of ES6 with limitations
• Preallocates all necessary memory and never calls malloc, realloc at run time. Upon OOM, the VM is halted
• Object pool, property pool, and string pool sizes are defined at compile time
• The minimal configuration takes only a few hundred bytes of RAM
• RAM usage: an object takes 6 bytes, each property: 16 bytes, a string: length + 6 bytes, any other type: 4 bytes
• Strings are byte strings, not Unicode. For example, 'ы'.length === 2, 'ы'[0] === '\xd1', 'ы'[1] === '\x8b'
• Limitations: max string length is 256 bytes, numbers hold 32-bit float value, no standard JS library
• mJS VM executes JS source directly, no AST/bytecode is generated
• Simple FFI API to inject existing C functions into JS

Example - blink in JavaScript on Arduino IDE ESP8266 Platform

#include <mjs3.h>                    

extern void myDelay(int x) { 
  delay(x);
}

extern void myDigitalWrite(int x, int y) {
  digitalWrite(x, y);
}

void setup() {
  pinMode(16, OUTPUT);                                  // Initialize the LED_BUILTIN pin as an output
  
  struct mjs *vm = mjs_create();                        // Create JS instance
  mjs_ffi(vm, "delay", (cfn_t) myDelay, "vi");          // Import delay()
  mjs_ffi(vm, "write", (cfn_t) myDigitalWrite, "vii");  // Import write()
  
  mjs_eval(vm, "while (1) { write(16, 0); delay(500); write(16, 1); delay(500); }", -1);
}

void loop() {
  //delay(1000);
}

Sketch uses 271568 bytes (26%) of program storage space. Maximum is 1044464 bytes.
Global variables use 27828 bytes (33%) of dynamic memory, leaving 54092 bytes for local variables. Maximum is 81920 bytes.

Supported standard operations and constructs

Name	Operation
Operations	All but !=, ==. Use !==, === instead
typeof	typeof(...)
delete	delete obj.k
while	while (...) {...}
Declarations	let a, b, c = 12.3, d = 'a';
Simple types	let a = null, b = undefined, c = false, d = true;
Functions	let f = function(x, y) { return x + y; };
Objects	let obj = {a: 1, f: function(x) { return x * 2}}; obj.f();
Arrays	let arr = [1, 2, 'hi there']

Unsupported standard operations and constructs

Name	Operation
Loops/switch	for (...) { ... },for (let k in obj) { ... }, do { ... } while (...), switch (...) {...}
Equality	==, != (note: use strict equality ===, !==)
var	var ... (note: use let ...)
Closures	let f = function() { let x = 1; return function() { return x; } };
Const, etc	const ..., await ... , void ... , new ..., instanceof ...
Standard types	No Date, ReGexp, Function, String, Number
Prototypes	No prototype based inheritance

Supported non-standard JS API

Function	Description
s[offset]	Return byte value at offset. s is either a string, or a number. A number is interprepted as uint8_t * pointer. Example: 'abc'[0] returns 0x61. To read a byte at address 0x100, use 0x100[0];.

LICENSE

Dual license: GPLv2 or commercial. For commercial licensing, please contact support@mongoose-os.com