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]));