Question

When I open jQuery’s source code I find this line.

var  // Will speed up references to window, and allows munging its name. window = this 

Why and how this line will speed up?

Answer 1

1. javascript functions have lexical scope
2. jQuery wraps its entire implementation in an anonymous function
3. when said function begins execution it is executing in the ‘global’ scope (ie this == window).

'window = this;' simply creates a local identifier in that scope so that references to it do not have to ‘bubble up’ outside of the local scope to resolve.