JS scope chain and closure

On closures, let's talk about scope chains first

js Scope contains overall situation and function Scope (es5)
Such as :

var a = 'global var'
function fn(){
	var b = 'function var';
	var n = function(){
		var c = 'inner function var'
	}
}
c //; undefined

Use Venn's diagram to describe the current scope division

Closures can be used to break through the scope chain

If you want to access the internal function in the global scope c Variable You need to use closures to connect it to the global scope

var a = 'global var'
function fn(){
	var b = 'function var';
	var n = function(){
		var c = 'inner function var'
		return c;
	}
	return n();
}
c = fn();
c;//  'inner function var'

Closure and GC

js gc use Reference count
In my submission Closures are used Reference count characteristic , bring Locally scoped variable references +1 Can't release