当检查 window 是否存在时，Web Worker 抛出异常

Question

我一直在与 web worker 打交道，我正在尝试创建一个 class ，当调用它时确定它是否可以在 worker 中执行它的工作或者是否在浏览器中实现。到目前为止，我有以下功能符合我的预期。

var workerClass = {
    getInstance: function()  {
        console.log("-- INSTANCE REQUESTED --")
        // If we have a worker we have an instance return this.
        if (this.worker !== undefined) return this.worker;
        console.log("-- INSTANCE NOT CACHED --")

        //var 
        //    iAmWorker = window === undefined,
        //    iCanBeAWorker = iAmWorker ? true : window.Worker !== undefined;

        var 
            iAmWorker = false,
            iCanBeAWorker = false;
        try{
            iAmWorker = window === undefined
            iCanBeAWorker = iAmWorker ? true : window.Worker !== undefined;
        }
        catch(e){
            iAmWorker = true;
            iCanBeAWorker = true;
        }

        if (!iAmWorker && iCanBeAWorker){
            console.log("-- I AM NOT IN A THREAD - SPAWNING ONE --")
            this.worker = {
                obj: new Worker("worker.js"),
                callFunc: function(funcName, Args){
                    // MAKE REQUEST
                    this.obj.postMessage([funcName,Args]);
                    this.obj.onmessage = function(e) {  
                        console.log('-- MESSAGE RECEIVED FROM WORKER THREAD --');
                        console.log(e.data);
                        // COMPLETE DEFFERED OBJ
                    };  
                    // RETURN DEFFERED OBJ
                }
            }
            console.log("-- I AM IN A THREAD --")
        }else{
            // Actual Worker object regardless of in a thread or not
            this.worker = {
                obj: this,
                callFunc: function(funcName, Args){
                    return this.obj[funcName](Args);
                }
            }
        }

        return this.worker;
    },

    // Return a Deferred Object
    workRequest: function(content){
        return this.getInstance().callFunc("actualWork",[content]);
    },

    // Actual Work
    actualWork: function(content){
        console.log("-- SIMULATING SOME WORK --")

        var dt = new Date();
        while ((new Date()) - dt <= 3000) { /* Do nothing */ }
        console.log("-- SIMULATED WORK DONE --");

        return content + " world";
    }
}

// NOTE ONLY EVER TO BE USED IN A WORKER 
onmessage = function(args) {
    postMessage(workerClass.getInstance().callFunc(
        args.data[0],
        args.data[1]
    ));
}

这样调用

workerClass.workRequest("Hello");

我的问题涉及以下内容。我知道工人 window 不存在。因此我尝试检查它的存在。

var 
    iAmWorker = window === undefined,
    iCanBeAWorker = iAmWorker ? true : window.Worker !== undefined;

这引发了一个我需要捕获的异常，我觉得这很丑陋而且很愚蠢。有没有更好的方法来实现这个测试？

干杯和感谢。

Answer 1

检查变量是否在当前范围内定义而没有任何异常风险的安全方法是使用 typeof:

if (typeof window !== "undefined") {
    // code that references window
} else {
    // code that does not reference window
}

或者，也许检查特定类型：

if (typeof window === "object") {
    // code that references window
} else {
    // code that does not reference window
}

当检查 window 是否存在时，Web Worker 抛出异常

Web Workers are throwing exceptions when window is checked for existance

javascript

web-worker