How to check if jQuery is Loaded

You can do any stuff before loading jQuery, the following code will help you to find out jQuery loaded or not.This method is not limited to jQuery only, you can check for any other variable or function in your javascript.

if (typeof jQuery == 'undefined') {

    // jQuery IS NOT loaded, do stuff here.

}

If jquery doesn't loaded, load jquery using javascript

if(!window.jQuery)
{
   var script = document.createElement('script');
   script.type = "text/javascript";
   script.src = "path/to/jQuery";
   document.getElementsByTagName('head')[0].appendChild(script);
}