JavaScript scripting engine Arduino IDE Library for ESP8266
ESP8266-Arduino-JavaScript is a Arduino IDE Library to implement a JavaScript engine for ESP8266 microcontroller.
- 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.
- 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,reallocat 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
#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.
| 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'] |
| 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 |
| 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];. |
Dual license: GPLv2 or commercial. For commercial licensing, please contact support@mongoose-os.com