javascript 实现 26 个字母加 10 个数字的 1-n 位数的任意组合，有没有能简写的写法？

config.js

'use strict';

module.exports = {
stringArr: ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'
],
urlLength: 4
}
---------------------------
index.js

let config = require('./config/config');
let arr = [];

function matchGroup(countLength) {
for (let i = 0; i < countLength; i++) {
if (i == 0) {
for (let j = 0; j < config.stringArr.length; j++) {
let reqUrl = 'http://www.' + config.stringArr[j] + '.com';
arr.push(reqUrl);
}
} else if (i == 1) {
for (let j = 0; j < config.stringArr.length; j++) {
for (let k = 0; k < config.stringArr.length; k++) {
let reqUrl = 'http://www.' + config.stringArr[j] + config.stringArr[k] + '.com';
arr.push(reqUrl);
}
}
} else if (i == 2) {
for (let j = 0; j < config.stringArr.length; j++) {
for (let k = 0; k < config.stringArr.length; k++) {
for (let l = 0; l < config.stringArr.length; l++) {
let reqUrl = 'http://www.' + config.stringArr[j] + config.stringArr[k] + config.stringArr[l] + '.com';
arr.push(reqUrl);
}
}
}
} else if (i == 3) {
for (let j = 0; j < config.stringArr.length; j++) {
for (let k = 0; k < config.stringArr.length; k++) {
for (let l = 0; l < config.stringArr.length; l++) {
for (let m = 0; m < config.stringArr.length; m++) {
let reqUrl = 'http://www.' + config.stringArr[j] + config.stringArr[k] + config.stringArr[l] + config.stringArr[m] + '.com';
arr.push(reqUrl);
}
}
}
}
}
........
}
}

matchGroup(config.urlLength);


console.log(arr);