Question

I tried doing it using the method below. However because jQuery has not been defined I get a –

ReferenceError: jQuery is not defined

from Firefox.

I was hoping it would have been undefined and testable not error producing.

If I define a dummy variable like this var jQuery, then when I use jQuery I will always be using that blank variable due to scope look-up rules.

How do I detect when the jQuery global variable is ready?

    // ... snip

    if (jQuery) { // not defined - I guess different from undefined - always errors

    // ...snip

Answer 1

if(window.jQuery !== undefined)

or

if(typeof jQuery !== 'undefined')

However, the first version is more readable in my opinion and in a browser environment window is the global object so window.X is pretty much equivalent to the global X – except the fact that trying to access an undefined window.X will not throw an error.