Easiest way to retrieve cross-browser XmlHttpRequest

Question

What is the easiest and safest way to retrieve XmlHttpRequest object that works across all browsers? Without any extra libraries. Is there a code snippet you use often?

P.S. I know there are tons of examples on the net, but this is precisely the reason I am asking: there are too many different examples, and I just want something simple and proven to work.

jQuery and other libraries is NOT an option. http://stackoverflow.com/questions/2450761/why-does-jquery-leak-memory-so-badly

Answer 1

I sometimes use this snippet from quirksmode.org

But only if there's a really good reason not to use a proper library ;)

function sendRequest(url,callback,postData) {
    var req = createXMLHTTPObject();
    if (!req) return;
    var method = (postData) ? "POST" : "GET";
    req.open(method,url,true);
    req.setRequestHeader('User-Agent','XMLHTTP/1.0');
    if (postData)
        req.setRequestHeader('Content-type','application/x-www-form-urlencoded');
    req.onreadystatechange = function () {
        if (req.readyState != 4) return;
        if (req.status != 200 && req.status != 304) {
//          alert('HTTP error ' + req.status);
            return;
        }
        callback(req);
    }
    if (req.readyState == 4) return;
    req.send(postData);
}

var XMLHttpFactories = [
    function () {return new XMLHttpRequest()},
    function () {return new ActiveXObject("Msxml2.XMLHTTP")},
    function () {return new ActiveXObject("Msxml3.XMLHTTP")},
    function () {return new ActiveXObject("Microsoft.XMLHTTP")}
];

function createXMLHTTPObject() {
    var xmlhttp = false;
    for (var i=0;i<XMLHttpFactories.length;i++) {
        try {
            xmlhttp = XMLHttpFactories[i]();
        }
        catch (e) {
            continue;
        }
        break;
    }
    return xmlhttp;
}

Answer 2

I just want something simple and proven to work.

Programmers compile working, tested, reliable, reusable code into what are called libraries or frameworks. Yet, you say yourself you don't want to use a library.

There is a list of Ajax frameworks on Wikipedia you can look at. I, and probably many other people. would recommend jQuery.

Answer 3

not 100% certain of your question - but if you're asking for function to return a cross browser XMLHTTP instance - we have used this in our native ajax library for years - and never a problem in any browser

function getXMLHTTP() {
    var alerted;
    var xmlhttp;
    /*@cc_on @*/
    /*@if (@_jscript_version >= 5)
    // JScript gives us Conditional compilation, we can cope with old IE versions.
    try {
        xmlhttp=new ActiveXObject("Msxml2.XMLHTTP")
    } catch (e) {
    try {
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP")
    } catch (E) {
        alert("You must have Microsofts XML parsers available")
    }
    }
    @else
        alert("You must have JScript version 5 or above.")
        xmlhttp=false
        alerted=true
    @end @*/
    if (!xmlhttp && !alerted) {
        // Non ECMAScript Ed. 3 will error here (IE<5 ok), nothing I can
        // realistically do about it, blame the w3c or ECMA for not
        // having a working versioning capability in  <SCRIPT> or
        // ECMAScript.
        try {
            xmlhttp = new XMLHttpRequest();
        } catch (e) {
            alert("You need a browser which supports an XMLHttpRequest Object")
      }
    }
    return xmlhttp
}

Hope this helps (sorry for uneven indents)