javascript document.getElementsByClassName compatibility with IE

Question

What is the best method to retrieve an array of elements that have a certain class?

I would use document.getElementsByClassName but IE does not support it.

So I tried Jonathan Snook's solution:

function getElementsByClassName(node, classname) {
    var a = [];
    var re = new RegExp('(^| )'+classname+'( |$)');
    var els = node.getElementsByTagName("*");
    for(var i=0,j=els.length; i<j; i++)
        if(re.test(els[i].className))a.push(els[i]);
    return a;
}
var tabs = document.getElementsByClassName(document.body,'tab');

...but IE still says:

Object doesn't support this property or method

Any ideas, better methods, bug fixes?

I would prefer not to use any solutions involving jQuery or other "bulky javascript".

Update:

I got it to work!

As @joe mentioned the function is not a method of document.

So the working code would look like this:

function getElementsByClassName(node, classname) {
    var a = [];
    var re = new RegExp('(^| )'+classname+'( |$)');
    var els = node.getElementsByTagName("*");
    for(var i=0,j=els.length; i<j; i++)
        if(re.test(els[i].className))a.push(els[i]);
    return a;
}
var tabs = getElementsByClassName(document.body,'tab');

...Also if you only need IE8+ support then this will work:

if(!document.getElementsByClassName) {
    document.getElementsByClassName = function(className) {
        return this.querySelectorAll("." + className);
    };
    Element.prototype.getElementsByClassName = document.getElementsByClassName;
}

Use it just like normal:

var tabs = document.getElementsByClassName('tab');

Answer 1

It's not a method of document:

function getElementsByClassName(node, classname) {
    var a = [];
    var re = new RegExp('(^| )'+classname+'( |$)');
    var els = node.getElementsByTagName("*");
    for(var i=0,j=els.length; i<j; i++)
        if(re.test(els[i].className))a.push(els[i]);
    return a;
}

tabs = getElementsByClassName(document.body,'tab');  // no document