load jQuery from external source if not loaded

Question

load jQuery from source

What I like to do is to drop my local jquery.js and have it hosted somewhere else. But what if Google is down? So let\'s cod

Answer 1

The problem with your script is that you're not waiting for the script to load before testing whether jQuery has been loaded. Use something like this instead:

function loadScript(src, callback) {
    var head=document.getElementsByTagName('head')[0];
    var script= document.createElement('script');
    script.type= 'text/javascript';
    script.onreadystatechange = function () {
        if (this.readyState == 'complete' || this.readyState == 'loaded') {
            callback();
        }
    }
    script.onload = callback;
    script.src = src;
    head.appendChild(script);
}

function isjQueryLoaded() {
    return (typeof jQuery !== 'undefined');
}

function tryLoadChain() {
    var chain = arguments;
    if (!isjQueryLoaded()) {
        if (chain.length) {
            loadScript(
                chain[0],
                function() {
                    tryLoadChain.apply(this, Array.prototype.slice.call(chain, 1));
                }
            );
        } else {
            alert('not loaded!');
        }
    } else {
        alert('loaded!');
    }
}

tryLoadChain(
    'https://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.min.js',
    'http://ajax.microsoft.com/ajax/jQuery/jquery-1.4.4.min.js',
    'mine.js');