Scope and Closure (iv) closures

Closures: functions defined inside a function

Why not output 200, go back to the last section of the scope chain problem, in the return function is not a,a as a free variable

Look for a in the parent scope, where the parent scope is the context in which the function is defined, not the context in which the execution occurs.

So find a F1 defined in the

1. Closure usage Scenarios

(1) function as the return value, as

(2) The function is passed as a parameter. Such as

Or the concept of a parent scope

Scope and Closure (iv) closures