ES6 const essence and completely immutable implementation (object.free)

The essence

const yes es6 Defined Constant ( After the definition Cannot be changed ) sign

But not completely unalterable

• about Basic types （ Numbers character string Boolean ） Can't change
  • because const What is saved is its content ( Or stack address More accurate )
• But for the The compound type （ Array object ）const Save a reference address
  • As long as the reference address remains unchanged, any internal properties of the object pointed to by the address can be modified at will

const arr = [];
arr.push(3);// ok
arr = [];// error

But it can be done and can't be changed at all

The key is to use Object.freeze
Implementation constants are completely immutable

var constancize = (obj) => {
	Object.freeze(obj);
	Object.keys(obj).forEach((key, i)=>{
		//  recursive   For objects with sub attributes   Conduct  freeze
		if(typeof obj[key] == 'object'){
			constancize(obj[key]);
		}
	})
}