js中的worker使用及多线程改单线程实现
一、Worker
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使用
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创建worker实例
var worker = new Worker(url); // 创建Worker对象
只会执行url指定的脚本,必须同源
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主线程
// 监听接收worker线程信息 worker.onmessage = (e) => console.log(`接收到worker传递的信息:${e.data}`); // 发送信息到worker线程 worker.postMessage('内容');
传递的数据类型包含:String、Number、Object、Array等JavaScript标准类型。
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worker线程
// 监听接收主线程信息 self.onmessage = (e) => console.log(`接收到主线程发送的信息:${e.data}`); // 发送信息到主线程 self.postMessage('内容');
在子线程中,self代表worker子线程的全局对象,也可以用this代替self,或者省略也行。
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销毁worker线程
worker.terminate() // 在主线程中关闭
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子线程自己关闭
self.close()
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示例
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主线程
// 创建Worker对象实例 var worker = new Worker('worker.js'); // 监听并接收worker线程消息 worker.onmessage = (e) => { console.log(`收到worker线程消息:${e.data}`); work.terminate(); // 销毁worker线程 }; // 向worker线程发送消息 worker.postMessage('hello worker')
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worker线程(worker.js)
// 监听并接收主线程发送的消息(省略self的写法) onmessage = (e) => { console.log(`收到主线程消息:${e.data}`); //向主线程发送消息 postMessage('你好,我是worker!'); }
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服务端
// 导入express const express = require('express') // 创建Web服务器 const app = express() // 调用express.static()方法,快速对外提供静态资源 app.use(express.static(__dirname)) app.listen(8080, () => { console.log('express server running at http://127.0.0.1:8080') })
启动服务端,浏览器访问http://127.0.0.1:8080即可,index.html页面中加载主线程js代码即可
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二、改写多线程为单线程执行
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代码
// btoa、atob方法实现 !function(){ // private property _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="; // public method for encoding this.btoa = function (input) { var output = ""; var chr1, chr2, chr3, enc1, enc2, enc3, enc4; var i = 0; input = _utf8_encode(input); while (i < input.length) { chr1 = input.charCodeAt(i++); chr2 = input.charCodeAt(i++); chr3 = input.charCodeAt(i++); enc1 = chr1 >> 2; enc2 = ((chr1 & 3) << 4) | (chr2 >> 4); enc3 = ((chr2 & 15) << 2) | (chr3 >> 6); enc4 = chr3 & 63; if (isNaN(chr2)) { enc3 = enc4 = 64; } else if (isNaN(chr3)) { enc4 = 64; } output = output + _keyStr.charAt(enc1) + _keyStr.charAt(enc2) + _keyStr.charAt(enc3) + _keyStr.charAt(enc4); } return output; } // public method for decoding this.atob = function (input) { var output = ""; var chr1, chr2, chr3; var enc1, enc2, enc3, enc4; var i = 0; input = input.replace(/[^A-Za-z0-9\+\/\=]/g, ""); while (i < input.length) { enc1 = _keyStr.indexOf(input.charAt(i++)); enc2 = _keyStr.indexOf(input.charAt(i++)); enc3 = _keyStr.indexOf(input.charAt(i++)); enc4 = _keyStr.indexOf(input.charAt(i++)); chr1 = (enc1 << 2) | (enc2 >> 4); chr2 = ((enc2 & 15) << 4) | (enc3 >> 2); chr3 = ((enc3 & 3) << 6) | enc4; output = output + String.fromCharCode(chr1); if (enc3 != 64) { output = output + String.fromCharCode(chr2); } if (enc4 != 64) { output = output + String.fromCharCode(chr3); } } output = _utf8_decode(output); return output; } // private method for UTF-8 encoding _utf8_encode = function (string) { string = string.replace(/\r\n/g, "\n"); var utftext = ""; for (var n = 0; n < string.length; n++) { var c = string.charCodeAt(n); if (c < 128) { utftext += String.fromCharCode(c); } else if ((c > 127) && (c < 2048)) { utftext += String.fromCharCode((c >> 6) | 192); utftext += String.fromCharCode((c & 63) | 128); } else { utftext += String.fromCharCode((c >> 12) | 224); utftext += String.fromCharCode(((c >> 6) & 63) | 128); utftext += String.fromCharCode((c & 63) | 128); } } return utftext; } // private method for UTF-8 decoding _utf8_decode = function (utftext) { var string = ""; var i = 0; var c, c1, c2, c3; c = c1 = c2 = 0; while (i < utftext.length) { c = utftext.charCodeAt(i); if (c < 128) { string += String.fromCharCode(c); i++; } else if ((c > 191) && (c < 224)) { c2 = utftext.charCodeAt(i + 1); string += String.fromCharCode(((c & 31) << 6) | (c2 & 63)); i += 2; } else { c2 = utftext.charCodeAt(i + 1); c3 = utftext.charCodeAt(i + 2); string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63)); i += 3; } } return string; } }() // 主线程 function Worker(jscode){ // 与之关联的子线程 this.self = new Worker_self(atob(jscode)) // 子线程与主线程关联 this.self.main = this } Worker.prototype.onmessage = undefined; Worker.prototype.addEventListener = function (type, func, x){ switch (type){ case 'message': this.onmessage = func; break default: break } } Worker.prototype.postMessage = function (msg){ return this.self.onmessage({data: msg}) } Worker.prototype.terminate = function (){ } // 子线程 function Worker_self(jscode){ let self = this; let window = self; let globalThis = self; eval(jscode) } Worker_self.prototype.onmessage = undefined Worker_self.prototype.main = undefined Worker_self.prototype.postMessage = function (msg){ return this.main.onmessage({data: msg}) } Worker_self.prototype.addEventListener = function (type, func, x){ switch (type){ case 'message': this.onmessage = func; break default: break } } Worker_self.prototype.close = function (){}
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注意事项
- 在原有主线程代码前面,添加以上部分代码,手动实现Worker
- new Worker()实例化Worker对象时,不再传入url地址,而是经过base64编码后的子线程相关源码(子线程中统一采用self或者this这种写法,视情况补充改写)