javascript 可靠地检测脚本是否在 Web Worker 中执行
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/7931182/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Reliably detect if the script is executing in a web worker
提问by thomas
I am currently writing a little library in JavaScript to help me delegate to a web-worker some heavy computation .
我目前正在用 JavaScript 编写一个小库，以帮助我将一些繁重的计算委托给网络工作者。
For some reasons (mainly for the ability to debug in the UI thread and then run the same code in a worker) I'd like to detect if the script is currently running in a worker or in the UI thread.
由于某些原因（主要是为了能够在 UI 线程中进行调试，然后在工作线程中运行相同的代码），我想检测脚本当前是在工作线程中还是在 UI 线程中运行。
I'm not a seasoned JavaScript developper and I would like to ensure that the following function will reliably detect if I'm in a worker or not :
我不是经验丰富的 JavaScript 开发人员，我想确保以下函数能够可靠地检测到我是否在工作人员中：
function testenv() {
try{
if (importScripts) {
postMessage("I think I'm in a worker actually.");
}
} catch (e) {
if (e instanceof ReferenceError) {
console.log("I'm the UI thread.");
} else {
throw e;
}
}
}
So, does it ?
那么，是吗？
采纳答案by Channing
As noted there is an answer in another threadwhich says to check for the presence of a document object on the window. I wanted to however make a modification to your code to avoid doing a try/catch block which slows execution of JS in Chromeand likely in other browsers as well.
如前所述，另一个线程中有一个答案，它说要检查窗口上是否存在文档对象。然而，我想对您的代码进行修改，以避免执行 try/catch 块，这会减慢 Chrome 中 JS 的执行速度，并且可能在其他浏览器中也是如此。
EDIT: I made an error previously in assuming there was a window object in the global scope. I usually add
编辑：我之前在假设全局范围中有一个窗口对象时犯了一个错误。我通常添加
//This is likely SharedWorkerContext or DedicatedWorkerContext
window=this;
to the top of my worker loader script this allows all functions that use window feature detection to not blow up. Then you may use the function below.
到我的工作加载程序脚本的顶部，这允许使用窗口功能检测的所有功能不会爆炸。那么你就可以使用下面的函数了。
function testEnv() {
if (window.document === undefined) {
postMessage("I'm fairly confident I'm a webworker");
} else {
console.log("I'm fairly confident I'm in the renderer thread");
}
}
Alternatively without the window assignment as long as its at top level scope.
或者没有窗口分配，只要它在顶级范围内。
var self = this;
function() {
if(self.document === undefined) {
postMessage("I'm fairly confident I'm a webworker");
} else {
console.log("I'm fairly confident I'm in the renderer thread");
}
}
回答by borbulon
Quite late to the game on this one, but here's the best, most bulletproofy way I could come up with:
这个游戏已经很晚了，但这是我能想到的最好、最防弹的方法：
// run this in global scope of window or worker. since window.self = window, we're ok
if (typeof WorkerGlobalScope !== 'undefined' && self instanceof WorkerGlobalScope) {
// huzzah! a worker!
} else {
// I'm a window... sad trombone.
}
回答by skalee
Emscripten does:
Emscripten 执行以下操作：
// *** Environment setup code ***
var ENVIRONMENT_IS_NODE = typeof process === 'object' && typeof require === 'function';
var ENVIRONMENT_IS_WEB = typeof window === 'object';
var ENVIRONMENT_IS_WORKER = typeof importScripts === 'function';
var ENVIRONMENT_IS_SHELL = !ENVIRONMENT_IS_WEB && !ENVIRONMENT_IS_NODE && !ENVIRONMENT_IS_WORKER;
