函数内JavaScript函数调用的更快算法

完整的工作代码基于@MBo的出色优化。这通过了所有测试，网址为https://www.prewars.com/kata/the-maximum-sum-
value-of-ranges-challenge-
version/train/javascript

，我收集了这个问题的出处。

function maxSum(arr, ranges) {  var max = null;  var sums = [];  var sofar = 0;  for (var i = 0; i <= arr.length; i++) {    sums[i] = sofar;    sofar += arr[i];  }  for (var i = 0; i < ranges.length; i++) {    var sum = sums[ranges[i][1]+1] - sums[ranges[i][0]];    if (max === null || sum > max) {      max = sum;    }  }  return max;}