Understanding of closures of JS

js The scope of variables of is divided into global variables and local variables , Variables inside a function are called local variables

You can access global variables inside the function , But the variables inside the function cannot be accessed outside the function

Closures can solve the problem that variables inside functions cannot be accessed , And you can hide this variable , No direct external access

Closure ： The sub functions inside the function can access the local variables inside the function , So closures are also called functions inside functions

function f1(){
    
	var n=999;
　　function f2(){
    
　　　alert(n);
　　}　　
	return f2;
}
var result = f1();
result(); // 999