// 求数字的汉字形式

const dbnum = function(num) {
	num = parseInt(num, 10);
	if (!num || num < 0 || num > Number.MAX_SAFE_INTEGER) return;

	const str1 = "零一二三四五六七八九";
	const str2 = ["千", "百", "十", ""];
	const str3 = ["兆", "亿", "万", ""];
	const reg1 = /\d{1,4}(?=(\d{4})+$)/g;
	const toChinese = function(num) {
		return [...num]
			.map(
				(num, index, arr) =>
					str1[num] +
					(num === "0" ? "" : str2[str2.length - arr.length + index])
			)
			.join("")
			.replace(/零+/, "零")
			.replace(/零$/, "");
	};
	console.log(String(num).replace(reg1, "$&,"));
	return String(num)
		.replace(reg1, "$&,")
		.split(",")
		.map((num, index, arr) => {
			return toChinese(num) + str3[str3.length - arr.length + index];
		})
		.join("");
};

console.log(dbnum(1001018000));

// 数组元素 组成的最大值问题
// @author luxueyan

var a = [7, 998, 9, 52, 5, 3]
var maxL = Math.max.apply(null, a).toString().length

var maxNumber = a.map(function(v) {
    return { diff: (v + new Array(maxL).join(v.toString().slice(0, 1))).slice(0, maxL), origin: v }
}).sort(function(v1, v2) {
    return v2.diff - v1.diff
}).map(function(v) {
    return v.origin
}).join('')

console.log(maxNumber)