【JS面试题】数组去重（6种方法）震惊面试官

let arr = [3, 7, 9, 1, 3, 2, 1, 1, 7]

let arr = [3, 7, 9, 1, 2]

function removeRepeat1(arr) {    return Array.from(new Set(arr))}

function removeRepeat2(arr) {    return [...new Set(arr)]}

function removeRepeat3(arr) {    let new_arr = []
    for(let i in arr) {
        let item = arr[i]
        if(new_arr.indexOf(item) === -1) {            new_arr.push(item)        }    }
    return new_arr}

function removeRepeat4(arr) {    let new_arr = []
    for(let i in arr) {
        let item = arr[i]
        if(!new_arr.includes(item)) {            new_arr.push(item)        }    }
    return new_arr}

function removeRepeat5(arr) {    return arr.filter((value, index) => {        return arr.indexOf(value) === index    })}

function removeRepeat6(arr) {
    let map = new Map()    let new_arr = []
    for(let i in arr) {                let item = arr[i]
        if(!map.has(item)) {            map.set(item, true)            new_arr.push(item)        }    }
    return new_arr}