js、es6 數據格式轉換總結

1、在數組中添加對象，push()

let arr = [{a:1}]
let obj = {
	b:2
}
arr.push(obj)	//數組新增對象	

2、數組轉換成字符串，並且用指定符合分割，join()

var joinArr = ["hello","world"];
var joinArr1 = joinArr.join(","); // joinArr1: "hello,world"

3、字符串轉換成數組，split()

var str = "hello,world"
var arr = str.split(",")	//此處有個坑，如果str沒有值，arr也會加個,變成髒數據，所以我一般加個三元運算符
var arr = str ? str.split(",") : []		

4、數組對象轉換成字符串，JSON.stringify

var data = JSON.stringify(data)	

5、字符串轉換成數組對象，JSON.parse

var data = JSON.parse(data)	

6、合併對象，Object.assign

const target = { a: 1, b: 1 };
const source1 = { b: 2, c: 2 };
const source2 = { c: 3 };
Object.assign(target, source1, source2);
target // {a:1, b:2, c:3}	//如果對象有同名屬性，後面的屬性會覆蓋前面的屬性

7、合併數組

var arr1 = [1, 2, 3];
var arr2 = ["a","b","c","d","e","f"];
//	1、concat方法
var arr = arr1.concat(arr2);  // [1, 2, 3, "a", "b", "c", "d", "e", "f"]
//  2、 通過for循環
for(let i in arr1){
    arr2.push(arr[i]);
}
console.log(arr2)  // [1, 2, 3, "a", "b", "c", "d", "e", "f"]
//  3、通過map()
arr1.map(item=>{
   arr2.push(item) 
});
console.log(arr2)  // [1, 2, 3, "a", "b", "c", "d", "e", "f"]
//  4、apply
arr1.push.apply(arr1,arr2);   
console.log(arr1)  // [1, 2, 3, "a", "b", "c", "d", "e", "f"] 
//  5、ES6 – 擴展運算符
arr = [...arr1,...arr2]
console.log(arr)   // [1, 2, 3, "a", "b", "c", "d", "e", "f"]

8、合併數組去重

 let arr1 = [1, 1, 2, 3, 6, 9, 5, 5, 4]
 let arr2 = [1, 2, 5, 4, 9, 7, 7, 8, 8]
 function uniqueArr(arr1,arr2) {
     //合併兩個數組
     arr1.push(...arr2)//或者arr1 = [...arr1,...arr2]
     //去重
     let arr3 = Array.from(new Set(arr1))//let arr3 = [...new Set(arr1)]
     console.log(arr3) 
 } 
 uniqueArr(arr1,arr2)

9、合併數組，並根據對象中id的值去重

//數組1
let arr1 = [
 {
       id: 1,
       name: "張三",
       age: 18
     },
     {
       id: 2,
       name: "李四",
       age: 18
     },
     {
       id: 3,
       name: "王五",
       age: 18
     }
   ];
   // 數組2
   let arr2 = [
     {
       id: 1,
       name: "張三"
     },

     {
       id: 2,
       name: "李四"
     }
   ];
   arr1.push(...arr2);    //合併數組
let hash = {}; //去重
let arr = arr1.reduce((preVal, curVal) => {
  hash[curVal.id]		//id就是數組中的id字段
    ? ""
    : (hash[curVal.id] = true && preVal.push(curVal));
  return preVal;
}, []);
console.log(arr);	//此處數組根據id去重可參考我上一篇文章，這裏就不細說了。