重用XMTHttpRequest对象? [英] Reusing XMTHttpRequest object?

问题描述

我正在尝试重写一些Ajax代码，以使其更适合自动完成需求.在这种情况下，有时您必须中止先前的请求 xhr.abort()，因此重用该 XMLHttpRequest 对象(我简称为xhr 此处).

I am trying to rewrite some ajax code to make it fit better with the needs for autocomplete. In that situation you have to abort a previous request sometimes, xhr.abort(), so it feels rather natural to reuse that XMLHttpRequest object (which I just called xhr here).

我试图了解重用 XMLHttpRequest 对象是个好主意.您会看到哪些利弊?

I am trying to understand whether it is a good or bad idea to reuse the XMLHttpRequestobject. What pros and cons can you see?

PS:此重写将使用本机ES6样式的Promise，因此只能在较新的Web浏览器中运行.

PS: This rewrite will use native ES6-style Promise so it can only run in newer web browsers.

推荐答案

就像@Bergi所建议的计时测试一样:

Just a timing test as @Bergi suggested:

function initCache(url) {
    var xhr = new XMLHttpRequest();
    xhr.open("get", url); xhr.send();
    console.log("Initialized cache");
}

function reuseXhr(url, numLoops) {
    var xhr = new XMLHttpRequest();
    for (var i=0; i<numLoops; i++) {
        xhr.open("get", url); xhr.send();
    }
    xhr.abort();
}

function newXhr(url, numLoops) {
    var xhr;
    for (var i=0; i<numLoops; i++) {
        xhr = new XMLHttpRequest();
        xhr.open("get", url); xhr.send(); xhr.abort();
    }
}
function testIt() {
    var url = "http://urlwithcors.com/"; // Pseudo-URL with CORS enabled
    var numLoops = 1000;
    initCache(url);
    setTimeout(function(){
        console.time("reuse"); reuseXhr(url, numLoops); console.timeEnd("reuse");
        console.time("new"); newXhr(url, numLoops); console.timeEnd("new");
    }, 5000);
}
testIt();

在Chrome中，这里的结果是:

The result here, in Chrome, is:

test-xhr-reuse.js:6 XHR finished loading: GET ...
reuse: 510.000ms
new: 386.000ms

所以...在慢速的PC上每次通话0.1毫秒，这不值得麻烦...

So... 0.1 ms per call on a slow pc, it is not worth the trouble...

现在等待-重用xhr甚至更慢...不值得.;-)

Now wait - it is even slower to reuse xhr... Not worth it. ;-)

更多测试表明完全没有区别.这只是一个偶然的问题.

A bit more testing tells there is no difference at all. It is just a matter of chance.

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