JS 数字转化为千分位字符串

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

function format(num) {
  let [int, fraction = ''] = (num + '').split('.');
  let ans = '';
  const len = int.length;
  int = int.split('').reverse();
  for (let i = 0; i < len; i++) {
    if (i !== 0 && i % 3 === 0) {
      ans = int[i] + ',' + ans;
    } else {
      ans = int[i] + ans;
    }
  }

  if (fraction !== '') ans += '.' + fraction;

  return ans;
}

2. 数学运算

function format(num) {
  let n = num;
  let tmp = 0;
  let ans = '';
  do {
    // 123456.7 % 1000 => 456.6999999..
    mod = n % 1000;
    // 123456 / 1000 => 123.4567
    n /= 1000;
    // ~~456.6999999.. => 456
    tmp = ~~mod;
    ans = (n >= 1 ? `${tmp}`.padStart(3, '0') : tmp) + (ans === '' ? '' : ',' + ans);
  } while (n >= 1);

  const start = num + '';
  const idx = start.indexOf('.');
  if (idx > -1) ans += start.substring(idx);

  return ans;
}

3. 正则匹配

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

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');