Question

I think it has something to do with a function running in a difference scope from where the jquery library is not accessable (shown being called as the last parameter on the second line below)

var funcExpandHeight = container.animate({
    height: '300px'
}, 300, function () {});
foo.animate({
    height: 'show'
}, 300, funcExpandHeight);

Line one works, then crashes on 'f.easing[i.animatedProperties[this.prop]] is not a function'

Munging the lines up together as show below, and the operation completes successfully.

    foo.animate({
     height: 'show'
 }, 300, function () {
     container.animate({
         height: container[0].scrollHeight + 'px'
     }, 300, function () {})
 });

Answer 1

Third argument of .animate() is callback function, but in your first code you’re just passing a variable.

var funcExpandHeight = function() {
   container.animate({height: '300px'}, 300, function(){});
}
foo.animate({height: 'show'}, 300, funcExpandHeight);

---

NOTE

config of .animate() is like following:

.animate( properties [, duration] [, easing] [, complete] )

Where [] means optional.

In your code, you don’t give the easing so, the third argument will treat as complete callback function.

For more detail see above link.