为什么我应该由 setTimeout 安排的函数调用会立即执行? [英] Why is my function call that should be scheduled by setTimeout executed immediately?

问题描述

这是我的问题.我有这个功能来测试代理服务器.

Here's my issue. I have this function to test proxy servers.

function crawl() {
    var oldstatus = document.getElementById('status').innerHTML;
    document.getElementById('status').innerHTML = oldstatus + "Crawler Started...<br />";
    var url = document.getElementById('url').value;
    var proxys = document.getElementById('proxys').value.replace(/
/g,',');

    var proxys = proxys.split(",");

    for (proxy in proxys) {
        var proxytimeout = proxy*10000;
        setTimeout(doRequest(url,proxys[proxy]), proxytimeout);
    }
}

我希望在大约 10 秒的间隔内调用 'doRequest()' 函数，但即使使用 setTimeout() 函数也会立即调用.

I want the 'doRequest()' function to be called in roughly 10 second intervals but even with the setTimeout() the functions are called immediately.

欢迎提出任何想法，谢谢.

Any ideas are welcome, thanks.

PS:即使我为 'proxytimout' 设置了一个任意值，它也没有任何效果.

PS: Even if I put an arbitrary value for 'proxytimout' it has no effect.

推荐答案

当您以这种形式将函数提供给 setTimeout 时，该函数将被执行，而不是传递给 setTimeout.您可以通过三种方式使其发挥作用:

As you give the function to the setTimeout in that form, the function is executed instead of passed to the setTimeout. You have three alternatives to make it work:

首先给出函数，然后给出超时和参数作为最后一个参数:

Give first the function, then the timeout and the parameters as the last arguments:

setTimeout(doRequest, proxytimeout, url, proxys[proxy]);

或者只是写一个将被评估的字符串:

Or just write a string that will be evaluated:

setTimeout('doRequest('+url+','+proxys[proxy]+')', proxytimeout);

第三种风格是传递一个调用函数的匿名函数.请注意，在这种情况下，您必须在闭包中执行此操作以防止值在循环中更改，因此会有点棘手:

Third style is to pass an anonymous function that calls the function. Note that in this case, you have to do it in a closure to prevent the values from changing in the loop, so it gets a bit tricky:

(function(u, p, t) {
    setTimeout(function() { doRequest(u, p); }, t);
})(url, proxys[proxy], proxytimeout);

第二种格式有点老套，但如果参数是标量值(字符串、整数等)仍然有效.第三种格式有点不清楚，因此在这种情况下，第一种选项显然最适合您.

The second format is a bit hacky, but works nevertheless if the arguments are scalar values (strings, ints etc). The third format is a bit unclear, so in this case the first option will obviously work best for you.

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