danbeam's getElementsByClassName

document のプロパティとして実装してる。第二引数が "startFrom"

by ethertank

HTML

<div class="t">////////</div>
<p>modify from: <a href="https://github.com/danbeam/getElementsByClassName/blob/master/getElementsByClassName.js" title="getElementsByClassName.js at master from danbeam/getElementsByClassName - GitHub">getElementsByClassName.js at master from danbeam/getElementsByClassName - GitHub</a></p>

JavaScript

/**
* getElementsByClassName
* @fileOverview  An easy way to find DOM Nodes with a specific class
* @author        Dan Beam <[email protected]>
* @param         {string} className - the class we're looking for on DOM Nodes
* @param         {element} startFrom (optional) - a point in the DOM to start from
* @return        {array} results - any DOM Nodes that have the specified class
*/


if ('function' !== typeof document.getElementsByClassName) {
    // NOTE: HTMLElement will work in pretty much everything IE6+,
    // but IE6 DOM Nodes inherit directly from Object (lame, right?)
    ('undefined' !== typeof HTMLElement ? HTMLElement : Object).prototype.getElementsByClassName =
        document.getElementsByClassName = function (testClass, startFrom) {
            for (
                var i = -1,
                results = [],

                finder = new RegExp('(?:^|\\s)' + testClass+ '(?:\\s|$)'),

                a = startFrom &&
                    startFrom.getElementsByTagName && startFrom.getElementsByTagName('*') ||
                    document.all || document.getElementsByTagName('*'),

                l = a.length;
  
                ++i < l;

                finder.test(a[i].className) && results.push(a[i])
            );

        a = null; //memory management
        return results; //return the results of our query
    };
}


// test
var t = document.getElementsByClassName("t");
t[0].style.backgroundColor = "red";
alert(t.length);