js常用的数组去重

1、双for去重

Array.prototype.Duplicate = function() {
    let arr = this;
    for(let i = 0; i < arr.length-1; i++) {
    　　for (let j = i+1; j < arr.length; j++) {
        　　if (arr[i] == arr[j]) {
            　　arr.splice(j, 1);
            　　j--;  // 删除元素之后，需要将数组的长度也减1，否则无法去除掉后面相同的值.
        　　};
    　　};
    };
    return arr;
}

2、利用递归去重

Array.prototype.Duplicate = function() {
    let arr = this;
    arr.sort();
    function loop(index) {
        if (index > 1) {
            if (arr[index] == arr[index-1]) {
                arr.splice(index, 1);
            };
            loop(index-1);
        };
    };
    loop(arr.length-1);
    return arr;
}

3、利用对象去重

Array.prototype.Duplicate = function() {
    let arr = this;
    let obj = {}
    let arr2 = []
    for (let i = 0; i < arr.length; i++) {
        if (!obj[arr[i]]) {
            obj[arr[i]] = true;
            arr2.push(arr[i]);
        }
    };
    return arr2;
}

4、利用indexOf

Array.prototype.Duplicate = function() {
    let arr = this;
    let arr2 = []
    for (let i = 0; i < arr.length; i++) {
        if (arr2.indexOf(arr[i]) == -1) {
            arr2.push(arr[i]);
        }
    };
    return arr2;
}

5、利用es6 includes方法判断

Array.prototype.Duplicate = function() {
    let arr = this;
    let arr2 = [];
    for (let i = 0; i < arr.length; i++) {
        if (!arr2.includes(arr[i])) {
            arr2.push(arr[i]);
        }
    }
    return arr2
}