Add additional checking for angular source

[qetr1ck-op]

In my case I load angular.js from cdn before import of the module.
So main point is that you need to have additional checking to require the angular source.

[qetr1ck-op]

@douglasduteil
It would be great to merge this PR

[bashasm]

With variable hoisting the declaration of angular will be moved to the top of the file, which makes declare angular variable and set it to undefined. So the above condition fails, you need to have a different way to check whether angular is loaded or not

[qetr1ck-op]

Where do you see to assigning it to undefined? It's only a conditional.
It's widely popular in npm comunity for AMD/UMD/CommonsJs/ES6module support.

[bashasm]

I am referring to Variable hoisting
"Variable declarations, wherever they occur, are processed before any code is executed. The scope of a variable declared with var is its current execution context, which is either the enclosing function or, for variables declared outside any function"

MDN Reference https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/var

Please let me know if you think otherwise

[qetr1ck-op]

Are you really aware what require() do?)
It doesn't execute anything, just returns an entity(function in our case)

[qetr1ck-op]

And hoisting in this case would look like when interpretation be 3th line {...window.angular: undefined} or a function if it was required early.