数组的全排列

        var list = [];
        var testArr = [1, 2, 3];
        function fullArangement(arr, n) {
            for (var i = n; i < arr.length; i++) {
                transposition(arr, i, n);
                n + 2 < arr.length ? fullArangement(arr, n + 1) : list.push(Object.assign([], arr));
                //或JSON.parse(JSON.stringify(arr)) 从第n+1个开始全排列 
                transposition(arr, i, n);
            }
        }
        function transposition(arr, i, n) {
            i != n ? arr[i] = [arr[n], arr[n] = arr[i]][0] : "";
        }
        fullArangement(testArr, 0);