Function and implementation of closures

Closure function

A closure is a function that has access to variables within the scope of another function

The function of closures

1. You can access the variables inside the function outside the function
2. You can keep the value of a variable in memory all the time

Disadvantages of closures

Because the variables in the function can always be stored in memory , So the memory consumption will be very large , Therefore, abusing closures may reduce the processing speed of programs , Cause problems such as memory consumption

Implementation of closure function

A common way to create closures ：
A function A Create another function inside b, By function b Access the local variables of this function , And then the function a Return function b, Execute function a, You can access the function a Local variables of .
Will perform a The result of is assigned to c, that c It's a closure .