Question

So say I had an array of $.post functions

var pa = [$.post(url0), $.post(url1),......];

$.when(pa[0],pa[1],...]) // works as expected

but

$.when.apply(pa) // does not work

Answer 1

Function.prototype.apply requires the context as first argument (the object which serves as reference for this, in the called function)

So you can call it like

$.when.apply( null, pa );

I like to use a little “trickery” to avoid that every time. We can invoke Function.prototype.bind like

var when = Function.prototype.apply.bind( jQuery.when, null );

now, we indeed can call

when( pa ).done( /* ... */ ) { }