将数字转化为“千分” xxx,xxx 形式的字符串的几种方法

 

1. 字符串操作

 1 function format(num) {
 2   let [int, fraction = ''] = (num + '').split('.');
 3   let ans = '';
 4   const len = int.length;
 5   int = int.split('').reverse();
 6   for (let i = 0; i < len; i++) {
 7     if (i !== 0 && i % 3 === 0) {
 8       ans = int[i] + ',' + ans;
 9     } else {
10       ans = int[i] + ans;
11     }
12   }
13 
14   if (fraction !== '') ans += '.' + fraction;
15 
16   return ans;
17 }

2. 数学运算

 1 function format(num) {
 2   let n = num;
 3   let tmp = 0;
 4   let ans = '';
 5   do {
 6     // 123456.7 % 1000 => 456.6999999..
 7     mod = n % 1000;
 8     // 123456 / 1000 => 123.4567
 9     n /= 1000;
10     // ~~456.6999999.. => 456
11     tmp = ~~mod;
12     ans = (n >= 1 ? `${tmp}`.padStart(3, '0') : tmp) + (ans === '' ? '' : ',' + ans);
13   } while (n >= 1);
14 
15   const start = num + '';
16   const idx = start.indexOf('.');
17   if (idx > -1) ans += start.substring(idx);
18 
19   return ans;
20 }

3. 正则匹配

1 function format(num) {
2   const reg = /\d{1,3}(?=(\d{3})+$)/g;
3   const [int, frac] = String(num).split('.');
4   return int.replaceAll(reg, '$&,') + '.' + frac;
5 }

4. Number.toLocaleString();

返回这个数字在特定语言环境下的表示字符串

let a = -1234567.8;
a.toLocaleString('en-us');