编写一个函数sumRange，当给定两个整数FROM和TO时，它返回从FROM到TO的整数之和

Question

任何人都可以告诉我如何更好地编写此代码，让我的工作变得有点麻烦

function sumRange(from, to) {
      var f = from;
      var t = to;
      var result = from;
      if(to >= from) {
        while (to > from) {
          from ++;
          result += from;
        }
        return result;
      } else if (from > to) {
        result = to;
        while (from > to ) {
          to++;
          result += to;
        }
        return result;
      }

    }

Answer 1

a和b之间的整数之和为：

((b - a + 1) * (a + b)) / 2

请参阅http://mathworld.wolfram.com/ArithmeticSeries.html

以任何顺序处理参数：

function sumRange(a, b) {
    return ((Math.abs(b - a) + 1) * (a + b)) / 2;
}