Document.getElementByIdのnative/wrapper/aliasの実行速度をChrome 16.0.912.75上でconsole.timeにより計測する

gistfile1.js

/*jslint devel: true, browser: true, maxerr: 50, maxlen: 80, indent: 4 */
// Edition 2012-01-13
// Chrome 16.0.912.75(V8 3.6.6.15, WebKit 535.7(@103989)) on Windows 7 Home Premium SP1 64bit

(function executeTest(doc, LOOP) {
    'use strict';

    var body, iterator1, iterator2, iterator3, iterator4, $id, getId, id,
        assign1, assign2, assign3, assign4;

    body = doc.body;
    iterator1 = iterator2 = iterator3 = LOOP;

    $id = function $id(elmId) {
        return doc.getElementById(elmId);
    };
    getId = doc.getElementById;
    id = doc.getElementById.bind(doc);

    body.parentNode.replaceChild(body.cloneNode(false), body);
    body = doc.body;
    body.id = 'test';

    console.time('Document.getElementById');
    while (iterator1) {
        iterator1 -= 1;
        assign1 = doc.getElementById('test');
    }
    console.timeEnd('Document.getElementById');

    console.time('Document.getElementById wrapper');
    while (iterator2) {
        iterator2 -= 1;
        assign2 = $id('test');
    }
    console.timeEnd('Document.getElementById wrapper');

    console.time('Document.getElementById + Function.call');
    while (iterator3) {
        iterator3 -= 1;
        assign3 = getId.call(doc, 'test');
    }
    console.timeEnd('Document.getElementById + Function.call');

    console.time('Document.getElementById + Function.bind');
    while (iterator4) {
        iterator4 -= 1;
        assign4 = id('test');
    }
    console.timeEnd('Document.getElementById + Function.bind');
}(document, 1000000));

/*
    Document.getElementById:                 88ms
    Document.getElementById wrapper:         149ms
    Document.getElementById + Function.call: 147ms
    Document.getElementById + Function.bind: 503ms
*/