Sum all numbers in array until a certain value is reached-CodePudding

I'm writing a function and this is the last piece of the puzzle, which I thought would be easy to deal with, but after some unsuccessful tinkering with for and while loops, I tried looking it up online and still couldn't find an answer. I came across some obscure and complex solutions, but I think there should be a more straightforward way to solve this. For example, if I have an array

[1, 2, 3, 5, 7, 9]

And the argument is 10, the function should return 6 (1 2 3), because the sum of the values should be <= 10 (or whatever number is passed). If the argument is 4, the function should return 3 (1 2) and so on.

CodePudding user response：

You can use a for loop:

const arg = 10
const arr = [1, 2, 3, 5, 7, 9]
let res = 0;
const calc = (arr, limit) => {
  for (num of arr) {
    if (num   res > limit) {
      break;
    }
    res  = num;
  }
  return res;
}
console.log(calc(arr, arg))

CodePudding user response：

.reduce() each current value (cur) added to the accumulator (acc) and checked vs. the limit (max). If acc cur is less than limit then return acc cur, otherwise return acc. Added .sort() if the array happens to be out of order, as per Spectric's comment.

const array = [1,2,3,5,6,8];
const mixed = [0,7,3,8,2,1];
const A = 10;
const B = 15;
const closest = (arr, max) => {
  return arr.sort((a, b) => a - b).reduce((acc, cur) => 
    (acc   cur) > max ? acc : (acc   cur));  
}

console.log(closest(array, A));
console.log(closest(array, B));
console.log(closest(mixed, B));