check if jquery has been loaded, then load it if false

Does anyone know how to check if jquery has been loaded (with javascript) then load it if it hasnt been loaded.

something like

if(!jQuery) {     //load jquery file }

How do you check is jQuery loaded or not?

Basically, the most reliable way to check if jQuery has been loaded is to check typeof jQuery — it will return "function" if jQuery was already loaded on the page, or "undefined" if jQuery hasn't been loaded yet.

How do you check if page is loaded completely?

You can check the document. readyState property. From MDN: Returns "loading" while the document is loading, "interactive" once it is finished parsing but still loading sub-resources, and "complete" once it has loaded.

Maybe something like this:

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