json.stringify()与json.parse()的区别以及用处

let arr = [1,2,3];
JSON.stringify(arr);//'[1,2,3]'
typeof JSON.stringify(arr);//string

let string = '[1,2,3]';
console.log(JSON.parse(string))//[1,2,3]
console.log(typeof JSON.parse(string))//object

let a = '["1","2"]';
let b = "['1','2']";
console.log(JSON.parse(a));// Array [1,2]
console.log(JSON.parse(b));// 报错

//判断数组是否包含某对象
let data = [
  {name:'掘金'},
  {name:'css学习'},
  {name:'js学习'},
  ],
  val = {name:'掘金'};
JSON.stringify(data).indexOf(JSON.stringify(val)) !== -1; // true

//判断两数组/对象是否相等
let a = [1,2,3],
  b = [1,2,3];
JSON.stringify(a) === JSON.stringify(b);//true

//存
function setLocalStorage(key,val){
  window.localStorage.setItem(key,JSON.stringify(val));
};
//取
function getLocalStorage(key){
  let val = JSON.parse(window.localStorage.getItem(key));
 window.localStorage.removeItem(key)
  return val;
};
//测试
let data = [
  {name:'掘金'},
  {name:'css学习'},
  {name:'js学习'},
  ];
setLocalStorage('STORAGEDATE',data);
let a = getLocalStorage('STORAGEDATE'); 

//深拷贝
function deepClone(data) {
  let _data = JSON.stringify(data),
    dataClone = JSON.parse(_data);
  return dataClone;
};
//测试
let arr = [1,2,3],
  _arr = deepClone(arr);
arr[0] = 2;
console.log(arr,_arr)//[2,2,3] [1,2,3]