how to find how many items need to sum to get given sum in array javascript

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I have array

var array = [4,2,6,8,1,6,5,2];
var samNeeded = 20;

as above i need to get how many items need to sum from start of the array to get sum needed

example needed output

var output = [4,2,6,8]

as first four items need to sum up to get the total 20

3 thoughts on “how to find how many items need to sum to get given sum in array javascript”

  1. Here is my solution:

    const array = [4, 2, 6, 8, 1, 6, 5, 2];
const sumNeeded = 20;

let auxSum = 0;
const res = [];

for (let i = 0; i < array.length; i++) {
  if (auxSum >= sumNeeded) break;
  auxSum += array[i];
  res.push(array[i]);
}

console.log(res);
    Reply

  2. Not sure this is the best approach, but it works for your example:

    const array = [4,2,6,8,1,6,5,2];
const samNeeded = 20;

let sum = 0;
const result = [];

// as long as array still has items and we haven't reached the target sum…
while (array.length && sum < samNeeded) {
  result.push(array.shift()); // consume the next item of the input array
  sum += result[result.length - 1]; // add it to sum as we go.
}

// it's not clear from your question whether you need the number of items…
console.log(result.length);

// or the items themselves:
console.log(result);
    Reply

  3. You could use Array#reduce.

    var array = [4,2,6,8,1,6,5,2];
var sumNeeded = 20;
let [res] = array.reduce(([res, sum],curr)=>
    [res.concat(sum >= sumNeeded ? []: curr), sum + (sum >= sumNeeded ? 0: curr)],
    [[], 0]);
console.log(res);
    Reply

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