数字 Number

数字千分位分割

function commafy(num) {
  return (num.toString().indexOf('.') !== -1) ? num.toLocaleString() : num.toString().replace(/(\d)(?=(?:\d{3})+$)/g, '$1,')
}

生成随机数

function randomNum(min, max) {
  switch (arguments.length) {
    case 1:
      return parseInt(Math.random() * min + 1, 10)
    case 2:
      return parseInt(Math.random() * (max - min + 1) + min, 10)
    default:
      return 0
  }
}

大整数加法

export default function add(a, b) {
    let i = a.length - 1;
    let j = b.length - 1;
    let carry = 0;
    let ret = '';
    while (i >= 0 || j >= 0) {
        let x = 0;
        let y = 0;
        let sum;
        if (i >= 0) {
            x = a[i] - '0';
            i--;
        }
        if (j >= 0) {
            y = b[j] - '0';
            j--;
        }
        sum = x + y + carry;
        if (sum >= 10) {
            carry = 1;
            sum -= 10;
        } else {
            carry = 0;
        }
        ret = sum + ret;
    }
    if (carry) {
        ret = carry + ret;
    }
    return ret;
}

// add('1', '999')
// add('999', '1')
// add('99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999', '1')