var arr = [1, 21, 2, 1, 4, 3, 3, 5, 7, 5];
//创建一个新数组 newArr=[]
//方法一:newArr.indexof(ele)==-1 push
function unique(arr) {
let newArr = [];
let len = arr.length;
for (let i = 0; i < len; i++) {
if (newArr.indexOf(arr[i]) == -1) {
newArr.push(arr[i])
}
}
return newArr;
}
console.log(unique(arr))
//方法二:借助对象 obj={}, 对象不会有相同的属性名
function unique2(arr) {
let newArr = [];
let obj = {};
let len = arr.length;
for (let i = 0; i < len; i++) {
if (!obj[arr[i]]) {
newArr.push(arr[i])
obj[arr[i]] = 1
}
}
return newArr;
}
console.log(unique2(arr))