实现千位分隔符

文章链接

      const a = 12345678910
      const b = 123456.789

      console.log(a.toLocaleString()) // 12,345,678,910
      console.log(b.toLocaleString()) // 123,456.789

      function numFormat(num, format = '_') {
        // 小于一千直接返回
        if (num < 1000) {
          return num
        }

        let str = num + ''
        const strList = str.split('.')
        const strMin = strList[1] ? `.${strList[1]}` : ''
        // 只针对整数部分
        if (strMin) {
          str = strList[0]
        }

        // 提示：从后面插入，不会影响前面的索引
        // 12345678910
        // 12345678_910
        // 12345_678_910
        // 12_345_678_910

        let flag = 0
        const list = Array.from(str)
        for (let i = list.length - 1; i > 0; i--) {
          flag++
          if (flag === 3) {
            list.splice(i, 0, format)
            flag = 0
          }
        }

        return list.join('') + strMin
      }

      console.log(numFormat(a, '__'))
      console.log(numFormat(b, '__'))
      console.log(numFormat(999))
      console.log(numFormat(1000))
      console.log(numFormat(1234))
      console.log(numFormat(12345))
      console.log(numFormat(123456))
      console.log(numFormat(1234567))
      console.log(numFormat(12345678))
      console.log(numFormat(123456789))
      console.log(numFormat(1234567890.1234))