JS学习-PromiseWorker

PromiseWorker

PromiseWorker是一个ChromeWorker，调用而不是postMessage()发送消息，而是调用post()，它返回一个Promise。

PromiseWorker模块由两个JavaScript文件PromiseWorker.jsm和PromiseWorker.js组成。

eg: https://github.com/Noitidart/PromiseWorker

PromiseWorker.jsm

PromiseWorker.jsm提供BasePromiseWorker。

Path: 'resource://gre/modules/PromiseWorker.jsm'

PromiseWorker.js

PromiseWorker.js提供AbstractWorker。

Path: 'resource://gre/modules/workers/PromiseWorker.js'

worker.js

importScripts('resource://gre/modules/workers/require.js');

let PromiseWorker = require('resource://gre/modules/workers/PromiseWorker.js');

// Instantiate AbstractWorker (see below).

let worker = new PromiseWorker.AbstractWorker()

worker.dispatch = function(method, args = []) {

	// Dispatch a call to method `method` with args `args`

	return self[method](...args);

};

worker.postMessage = function(...args) {

	// Post a message to the main thread

	self.postMessage(...args);

};

worker.close = function() {

	// Close the worker

	self.close();

};

worker.log = function(...args) {

	// Log (or discard) messages (optional)

	dump('Worker: ' + args.join(' ') + '\n');

};

// Connect it to message port.

self.addEventListener('message', msg => worker.handleMessage(msg));

main.js

const { utils: Cu } = Components;

const { BasePromiseWorker } = Cu.import('resource://gre/modules/PromiseWorker.jsm', {});

let myWorker = new BasePromiseWorker('path_to_worker_file.js');

post()

promise = myWorker.post(aFunctionName, [...args], aClosure, aTransferList);

//要传输ArrayBuffer对象，请将包含它的数组作为aTransferList参数传递。

myWorker.post('func', [buffer], null, [buffer]);

/*上面的代码也可以使用Meta对象完成。您要传输的每个特殊数据参数都可以包装在一个BasePromiseWorker.Meta对象中。*/

/* 传输单个值 */

myWorker.post('func', [new BasePromiseWorker.Meta(buffer, {transfers: [buffer]})]);

/* 传输多个值. transfers 指定要传输的值 */

new PromiseWorker.Meta({

	theBuf: aBuf,

	otherNonTrans: 'this string is not transfered but copied'},

	{transfers: [aBuf]

});

reject()

受支持的错误类型

* EvalError

* InternalError

* RangeError

* ReferenceError

* SyntaxError

* TypeError

* URIError

// Worker.js

// Define a custom error prototype.

function CustomError(message) {

	this.message = message;

}

CustomError.prototype.toMsg = function() {

	return {

		exn: 'CustomError',

		message: this.message,

	};

};

// A function called by message.

function func() {// Throw a custom error.

	throw new CustomError('meow');

}

// Main thread

// Define a custom error prototype.

function CustomError(message) {

	this.message = message;

}

CustomError.fromMsg = function(msg) {

	return new CustomError(msg.message);

};

// Register a constructor.

myWorker.ExceptionHandlers['CustomError'] = CustomError.fromMsg;

resolve()

function func(buffer) {

	// do something with buffer...

	return 1; // 1 is sent back to main thread, as a resolved promise.

}

巴特西