ES6 decoupling top-level objects from windows

What is a top-level object

Also called global object Globally accessible objects
Such as ： window.a = 123 a Is the top-level object
however , In the browser, the top-level object is window self,Node In Chinese, it means global

Top level objects and window The disadvantages of dependence

• Leading to easy abuse of top-level objects , Cause object conflict
  Such as You define a=2 And window.a =2 It's the same , It automatically becomes a variable mounted on the top-level object
• Not conducive to modularity ： The idea of modularity is Local definition Just want to expose the least content globally

es6 How to avoid top-level objects and window rely on

• Use const let And Block level action to avoid When declaring variables directly Hang up window

let b = 1;
window.b // undefined