es6常用数组格式转换

计算数组中所有值的总和

var numbers = [3,5,9];
        var sumValue = numbers.reduce(function(sum,number){ //sum2 前两个数的和
            console.log(sum) //1000 1003 1008
            return sum + number;
        },1000  )  //第一次初始化时用1000 + 数组中的第一项
        console.log(sumValue) //1017

将数组中对象的某个属性抽离到另一个数组中

var primaryColors = [
            {color:"red"},
            {color:"yellow"},
            {color:"bule"}
        ]
        var colorsArr = primaryColors.reduce(function(arr,primaryColor){
            arr.push(primaryColor.color);
            return arr;
        },[]);
        console.log(colorsArr)    //["red", "yellow", "bule"]

在数组中添加对象，push()

let arr = [{a:1}]
let obj = {
    b:2
}
arr.push(obj)

数组转换成字符串，并且用指定符合分割，join()

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

###字符串转换成数组，split()

var str = "hello,world"
var arr = str.split(",")    //此处有个坑，如果str没有值，arr也会加个,变成脏数据，所以我一般加个三元运算符
var arr = str ? str.split(",") : []

数组对象转换成字符串，JSON.stringify

var data = JSON.stringify(data)    

字符串转换成数组对象，JSON.parse

var data = JSON.parse(data)    

合并对象，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}    //如果对象有同名属性，后面的属性会覆盖前面的属性

过滤数组，arr.filter

// 1、去掉空数组空字符串、undefined、null

var arr = ['1','2',undefined, '3.jpg',undefined]
var newArr = arr.filter(item => item)
console.log(newArr)

var arr = ['1','2',null, '3.jpg',null]
var newArr = arr.filter(item => item)
console.log(newArr)

// 2、空字符串里面不能包含空格

var arr = ['1','2','', '3.jpg','']
var newArr = arr.filter(item => item)
console.log(newArr)

// 3、去掉数组中不符合项

var arr = [20,30,50, 96,50]
var newArr = arr.filter(item => item>40)  
console.log(newArr)

var arr = ['10','12','23','44','42']
var newArr = arr.filter(item => item.indexOf('2')<0) 
console.log(newArr)

// 4、数组去重

var arr = [1, 2, 2, 3, 4, 5, 5, 6, 7, 7,8,8,0,8,6,3,4,56,2];
var arr2 = arr.filter((x, index,self)=>self.indexOf(x)===index)  
console.log(arr2); //[1, 2, 3, 4, 5, 6, 7, 8, 0, 56]

// 5、两个数组取相同项

let arr = [{ id: 1, name: 'zs' }, { id: 2, name: 'ls' }, { id: 3, name: 'ww' }, { id: 4, name: 'xm' }, { id: 5, name: 'xh' },]
let sum = [3, 4, 5]
let newArr = arr.filter(item => sum.indexOf(item.id) > -1)
console.log(newArr)

合并数组

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、 通过for循环
for(let i in arr1){
    arr2.push(arr[i]);
}
console.log(arr2)  // [1, 2, 3, "a", "b", "c", "d", "e", "f"]
//  3、通过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 – 扩展运算符
arr = [...arr1,...arr2]
console.log(arr)   // [1, 2, 3, "a", "b", "c", "d", "e", "f"]

合并数组去重

 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) {
     //合并两个数组
     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)

合并数组，并根据对象中id的值去重

//数组1
let arr1 = [
 {
       id: 1,
       name: "张三",
       age: 18
     },
     {
       id: 2,
       name: "李四",
       age: 18
     },
     {
       id: 3,
       name: "王五",
       age: 18
     }
   ];
   // 数组2
   let arr2 = [
     {
       id: 1,
       name: "张三"
     },

     {
       id: 2,
       name: "李四"
     }
   ];

 arr1.push(...arr2);    //合并数组
let hash = {}; //去重
let arr = arr1.reduce((preVal, curVal) => {
  hash[curVal.id]        //id就是数组中的id字段
    ? ""
    : (hash[curVal.id] = true && preVal.push(curVal));
  return preVal;
}, []);
console.log(arr);

原文链接：https://blog.csdn.net/weixin_41698051/article/details/103602327