es6 filter() 数组过滤方法总结
1.创建一个数组，判断数组中是否存在某个值
var newarr = [
{ num: 1, val: 'ceshi', flag: 'aa' },
{ num: 2, val: 'ceshi2', flag: 'aa2' }
]
console.log(newarr.filter(item => item.num===2 ))
2.也可以通过上面方法过滤掉num为2的留下num为1的
var newarr = [
{ num: 1, val: 'ceshi', flag: 'aa' },
{ num: 2, val: 'ceshi2', flag: 'aa2' }
]
console.log(newarr.filter(item => item.num!=2 ))
3.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)
>//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)
4.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)
5.过滤不符合项
var arr = ['10','12','23','44','42']
var newArr = arr.filter(item => item.indexOf('2')<0)
console.log(newArr)
6.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]
7.数组去重es6
var arr=[1,2,1,'1',null,null,undefined,undefined,NaN,NaN]
let res=Array.from(new Set(arr));//{1,2,"1",null,undefined,NaN}
//or
let newarr=[...new Set(arr)]
8.数组对象去重es6
let person = [
{id: 0, name: "小明"},
{id: 1, name: "小张"},
{id: 2, name: "小李"},
{id: 3, name: "小孙"},
{id: 1, name: "小周"},
{id: 2, name: "小陈"},
];
let obj = {};
let peon = person.reduce((cur,next) => {
obj[next.id] ? "" : obj[next.id] = true && cur.push(next);
return cur;
},[]) //设置cur默认类型为数组，并且初始值为空的数组
console.log(peon);
// (4) [{…}, {…}, {…}, {…}]0: {id: 0, name: "小明"}1: {id: 1, name: "小张"}2: {id: 2, name: "小李"}3: {id: 3, name: "小孙"}length: 4__proto__: Array(0)
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