A brief discussion on closures in JS_Basic knowledge

( ⊙o⊙ )! ! ! This is too official. As a newbie, I can’t understand what it means! But as a curious newbie, I really want to know what "closure" is! So I finally found the legendary "Du Niang" to help! I still have a little understanding!

Personal opinion: Define another method function in the function body, and this method function is referenced by variables outside the function, then a closure is formed!

Maybe this understanding is too abstract and not so simple and easy to understand! Example:

Copy code The code is as follows:

The above code creates a closure, because when the function is executed to var C=A();, it seems that C points to function A, but in fact the function pointed to by C is function B. So when C() is executed, 2 will be output; in this case, function B is referenced by variables other than function A. Based on personal opinion, a closure is created!

When I learned about closures in a small way, I also looked at the uses of closures. It is said that there are two main uses of closures:

1. You can read the variables inside the function

2. Keep these variables in memory at all times

Copy code The code is as follows:

In the above code, C still points to function B. C is executed twice, and the first time it is output 1. The second output is 2, which proves that S has been saved in the memory and is not automatically cleared after the A function is called. Why is this? The reason is because the B function is assigned to a global variable. This As a result, function B has always been in memory, and the execution of function B needs to depend on function A, so A has always been in memory and will not be recycled after the call is completed! (This understanding seems a bit unprofessional)!

The expression is completed, please give us your advice!