js数组去重

 let arr1 = [1, 2, 3, 4, 1]

    //方法1:Array.filter() + indexOf

    var a = arr1.filter((item, index) => {
        return arr1.indexOf(item) === index
    })
    console.log(a);


    //方法2:利用includes方法
    let b = []
    for (let i of arr1) {
        !b.includes(i) && b.push(i)
    }
    console.log(b);

    //方法3:利用indexOf方法
    var c = [];
    for (var i = 0; i < arr1.length; i++) {
        if (c.indexOf(arr1[i]) == -1) { //没存在过就push进去
            c.push(arr1[i])
        }
    }
    console.log(c);

    //方法4:利用new Set  Array.from方法
    var d = new Set(arr1);
    var e = Array.from(d)

    console.log(e);


    //方法5:for...of + Object

    let f = []
    let obj = {}

    for (let i of arr1) {
        if (!obj[i]) {
            f.push(i)
            obj[i] = 1
        }
    }
    console.log(f)