关于javascript:js-数组全排列算法

      /**       * @function 数组排列组合       * [1,2,3] => 123 132 213 231 321 312       */      function permutationCombination(arr) {        if (arr.length === 1) {          return [arr];        }        const res = [];        arr.forEach((val, index) => {          const childArr = [...arr];          childArr.splice(index, 1);          res.push(            ...permutationCombination(childArr).map(item => [val, ...item])          );        });        return res;      }