javascript数组全排列,数组元素所有组合

function permute(input) {

  var permArr = [],

  usedChars = [];

  function main(input){

    var i, ch;

    for (i = 0; i < input.length; i++) {

      ch = input.splice(i, 1)[0];

      usedChars.push(ch);

      if (input.length == 0) {

        permArr.push(usedChars.slice());

      }

      main(input);

      input.splice(i, 0, ch);

      usedChars.pop();

    }

    return permArr

  }

  return main(input);

};

console.log(permute([5, 3, 7, 1]));