js数组去重

1.ES6 Set

    let arr = [1,2,3,3,"a","a","1"]
    arr = [...new Set(arr)] 
    console.log(arr)
    // [1, 2, 3, "a", "1"]

2.indexOf

    let arr = [1,2,3,3,"a","a","1"]

    function unique(array){
        if (!Array.isArray(arr)) {
            console.log('type error!')
            return
        }
        let temp = []; 
        for(let i = 0; i < array.length; i++){
            if(temp.indexOf(array[i]) == -1){
                temp.push(array[i]);
            }
        }
        return temp;
    }
    console.log(unique(arr))
    // [1, 2, 3, "a", "1"]

3.sort

    let arr = [1,2,3,3,"a","a","1"]

    function unique(array){
        if (!Array.isArray(arr)) {
            console.log('type error!')
            return
        }
        array.sort();
        let temp = [array[0]]; 
        for(let i = 0; i < array.length; i++){
            if(array[i] !== temp[temp.length-1]){
                temp.push(array[i]);
            }
        }
        return temp;
    }
    
    console.log(unique(arr))
    // [1, 2, 3, "a", "1"]

4.for循环

    let arr = [1,2,3,3,"a","a","1"]
    function unique(array){
        if (!Array.isArray(arr)) {
            console.log('type error!')
            return
        }
        let temp = [];
        for(let i = 0; i < array.length; i++) {
            for(let j = i + 1; j <array.length; j++){
                if (array[i] === array[j]){
                    i++;
                    j = i;
                }
            }
            temp.push(array[i]);
        }
        return temp;
    }
    console.log(unique(arr))
    // [1, 2, 3, "a", "1"]

5.includes

    let arr = [1,2,3,3,"a","a","1"]
    function unique(array){
        if (!Array.isArray(arr)) {
            console.log('type error!')
            return
        }
        let temp = [];
        for(let i = 0; i < array.length; i++) {
            if(!temp.includes(array[i])){
                 temp.push(array[i]);
            }
           
        }
        return temp;
    }
    console.log(unique(arr))
    // [1, 2, 3, "a", "1"]

6.对象

    let arr = [1,2,3,3,"a","a","1"]
    // 判断是否为js对象键时，会自动对传入的键执行“toString()”
    function unique(array){
        if (!Array.isArray(arr)) {
            console.log('type error!')
            return
        }
        let temp = {}, temp1 = [],  val, type;
        for (let i = 0; i < array.length; i++) {
            val = array[i];
            type = typeof val;
            if (!temp[val]) {
                temp[val] = [type];
                temp1.push(val);
            } else if (temp[val].indexOf(type) < 0) {
                temp[val].push(type);
                temp1.push(val);
            }
        }
        return temp1;
    }
    console.log(unique(arr))
    // [1, 2, 3, "a", "1"]

7.ndexOf与下标

    let arr = [1,2,3,3,"a","a","1"]
    function unique(array){
        if (!Array.isArray(arr)) {
            console.log('type error!')
            return
        }
        let temp = [];
        for(let i = 0; i < array.length; i++) {
            if(array.indexOf(array[i]) == i){
                temp.push(array[i])
            }
        }
        return temp;
    }
    console.log(unique(arr))
    // [1, 2, 3, "a", "1"]