question/add-comma-to-number

[giscus[bot]]

question/add-comma-to-number

北美前端面试攻略

https://us-fe.github.io/question/add-comma-to-number.html

[xiaoyu2er]

方法二 正则 https://stackoverflow.com/a/2901298/5755195

/**
 * @param {number} num
 * @return {string}
 */
function addComma(x) {
      return x.toString().replace(/\B(?<!\.\d*)(?=(\d{3})+(?!\d))/g, ",");
}

console.log(addComma(1)) // '1'
console.log(addComma(1000)) // '1,000'
console.log(addComma(-12345678)) // '-12,345,678'
console.log(addComma(12345678.12345)) // '12,345,678.12345'
console.log(addComma(-.12345)) // '-0.1234'

相关解释可以看上面的链接，或者看 https://github.com/qdlaoyao/js-regex-mini-book 2.4.2 章节

[xiaoyu2er]

方法一 普通方法

/**
 * @param {number} num
 * @return {string}
 */
function addComma(num) {
  // your code here
  let [number, decimal] = num.toString().split('.');

  let str = '';
  let i = number.length - 1;
  let count = 0;
  while (i >= 0) {
    str = number[i] + str;
    count++;
    if (i > 0 && count % 3 === 0 && number[i -1] !== '-') {
      str = ',' + str;
    }
    i--;
  }
  return decimal ? str + "." + decimal : str

}

console.log(addComma(-123.1234))
console.log(addComma(-.1234))
console.log(addComma(123456789))
console.log(addComma(123456789.1234))