第一种方法　不兼容ie6低版本

var arr = [1, 2, 5, 8, 9, 1, 2, 8, 6, 7, 3, 9];
var res = [];
for (var i = 0; i < arr.length; i++) {
    if (res.indexOf(arr[i]) == -1) {
        res.push(arr[i]);
    }
}
console.log(res); // [1, 2, 5, 8, 9, 6, 7, 3]

 

第二种方法

var arr = [1, 2, 5, 8, 9, 1, 2, 8, 6, 7, 3, 9];
var obj = {
    1: true,
    2: true,
    5: true
};
if (!obj[arr[i]]) {
    res.push(arr[i]);
    obj[arr[i]] = true;
}
console.log(obj[i]);  // [1, 2, 5, 8, 9, 6, 7, 3]

自定义去重函数

var arr = [1, 2, 5, 8, 9, 1, 2, 8, 6, 7, 3, 9];
function noRepeat(array) {
    var obj = {};
    for (var i = 0; i < array.length; i++) {
        if (obj[array[i]]) {
            array[i] = array[array.length -1];
            array.length -= 1;
            i--;
            continue;
        }
        obj[array[i]] = true;
    }
    return array;
}
console.log(noRepeat(arr));  // [1, 2, 5, 8, 9, 6, 7, 3]

 

第三种方法　ES6数组去重

var arr = [1, 2, 5, 8, 9, 1, 2, 8, 6, 7, 3, 9];
let set = new Set(arr);
console.log([...set]);  // [1, ,2, 5, 8, 9, 6, 7, 3]