1  function fn1(arr, newArr) {
 2         newArr[0] = arr[0] //赋值新数组一个初始值
 3         for (let i = 0; i < arr.length; i++) {
 4             for (let k = 0; k < newArr.length; k++) {
 5                 if (arr[i] == newArr[k]) {
 6                     break;
 7                 }
 8                 if (k == newArr.length - 1) {
 9                     newArr.push(arr[i])
10                 }
11             }
12         }
13         return newArr
14     }
15 var arr = ['a', 'b', 3, 4, 'a', 4, 20, 8, 'c', 'c'];  
16 console.log(fn1(arr, newArr))

function fn2(arr) {
        for (let i = 0; i < arr.length; i++) {
            for (let k = i + 1; k < arr.length; k++) {
                if (arr[i] == arr[k]) {
                    arr.splice(k, 1);
                   
                }
            }
        }
        return arr;
    }