let arr = [12, 23, 34, 12, 12, 34, 56, 56, 56, 76]

方法一：set特性，数据不能重复

        function one() {
            let set = new Set(arr)
            let arr1 = [...set]
            console.log(arr1);
        }
        one()

方法二：数组indexOf==-1

		function two() {
            let arr1 = []
            for (let i = 0; i < arr.length; i++) {
                if (arr1.indexOf(arr[i]) == -1) {
                    arr1.push(arr[i])
                }
            }
            console.log(arr1);
        }
        two()

方法三：数组双重for循环+splice

		function three() {
            for (let i = 0; i < arr.length; i++) {
                for (let j = i + 1; j < arr.length; j++) {
                    if (arr[i] == arr[j]) {
                        arr.splice(j, 1)
                        j--;
                    }
                }
            }
            console.log(arr)
        }
        three()

方法四：对象属性特性

		function four() {
            let obj = {};
            let newArr = [];
            for (let i = 0; i < arr.length; i++) {
                if (obj[arr[i]]) {
                    obj[arr[i]]++
                } else {
                    obj[arr[i]] = 1
                    newArr.push(arr[i])
                }
            }
            console.log(newArr);
        }
        four()

…