Only load jQuery if not already present

21 June 2010

Very useful method of ensuring jQuery is loaded before running the code that needs it - from How to build a web widget (using jQuery) - Alex Marandon

[js] /******** Load jQuery if not present *********/ if (typeof jQuery === “undefined” || jQuery.fn.jquery !== ‘1.4.2’) { var script_tag = document.createElement(‘script’); script_tag.setAttribute(“type”,“text/javascript”); script_tag.setAttribute(“src”, “http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js") script_tag.onload = main; // Run main() once jQuery has loaded script_tag.onreadystatechange = function () { // Same thing but for IE if (this.readyState == ‘complete’ || this.readyState == ‘loaded’) main(); } document.getElementsByTagName(“head”)[0].appendChild(script_tag); } else { main(); } [/js]