JavaScript in a closed package

What is a closure package

The "official" explanation is that the so-called "closure" refers to an expression (usually a function) that has many variables and an environment in which these variables are bound, and therefore these variables are also part of the Expression.

Closure Code:

function A () {  var i=0;  Function b () {   alert (+ +i);     } return b;} var c=a (); c ();

There are two features of this code:

1. Function b is nested inside function a;

2. Function A returns function b;

So after the execution of Var c=a (), the variable c actually points to function b, after executing c () will pop up a window to show the value of I (the first time is 1), This short code creates a closure, why? Because the variable C outside of function A refers to function B in function a, that is:

when function A's intrinsic function B is referenced by a variable outside of function a, a closure is Created.

Defined:

If in an intrinsic function a reference is made to a variable outside the scope (but not at the global scope), then the intrinsic function is considered a closure.

Application Scenarios:

1. Security of variables within the protection Function. Function A can be accessed only by Function B and cannot be accessed by other means, thus protecting the security of I.

2. Maintains a variable in memory. Because of the closure, function A in I always exists in memory, so every time I execute C (), I will add 1.

JavaScript in a closed package