Is there a more efficient way to display the sum of two arrays using For Loops in JavaScript?

Question

I want the end result to display "276 + 351 = 627". Is there a more efficient way to do so while using for loops? This is a practice question I found online, so the stuff after the 2 arrays is what I've come up with.

let arr_1 = [3, 5, 22, 5,  7,  2,  45, 75, 89, 21, 2];
let arr_2 = [9, 2, 42, 55, 71, 22, 4,  5,  90, 25, 26];

let sum1 = 0;
let sum2 = 0;

for (let i = 0; i < arr_1.length; i++) {
    sum1 += arr_1[i];
}
for (let j = 0; j < arr_2.length; j++) {
    sum2 += arr_2[j];
}

let total = sum1 + sum2;

console.log(`${sum1} + ${sum2} = ${total}`);

Answer 1

The reduce function allows you to write it in a very short manner:

 const arr_1 = [3, 5, 22, 5, 7, 2, 45, 75, 89, 21, 2], arr_2 = [9, 2, 42, 55, 71, 22, 4, 5, 90, 25, 26], add = arr => arr.reduce((sum, n) => sum + n), sum1 = add(arr_1), sum2 = add(arr_2), total = sum1 + sum2; console.log(`${sum1} + ${sum2} = ${total}`);

Answer 2

There many way to loop through a array if you read the MDN Docs Link Here . One of the way is reduce() which work with almost all browsers but i would prefer to use forEach() as it is one of oldest proto on arrays.. and here is how it is done

let arr_1 = [3, 5, 22, 5, 7, 2, 45, 75, 89, 21, 2];
let arr_2 = [9, 2, 42, 55, 71, 22, 4, 5, 90, 25, 26];

let sum1 = 0
let sum2 = 0
let total = 0

arr_1.forEach((el) => {
  sum1 += el
});
arr_2.forEach((el) => {
  sum2 += el
});
total = sum1 + sum2

console.log(`${sum1} + ${sum2} = ${total}`);

JSFiddle Link

Answer 3

this way

 const doSum = arr => arr.reduce((a,c)=>a+c,0) // let zero value, if arr is empty, arr_1 = [ 3, 5, 22, 5, 7, 2, 45, 75, 89, 21, 2 ], arr_2 = [ 9, 2, 42, 55, 71, 22, 4, 5, 90, 25, 26 ], sum1 = doSum(arr_1), sum2 = doSum(arr_2), total = sum1 + sum2; console.log(`${sum1} + ${sum2} = ${total}`)

Answer 4

Assuming both arr_1 and arr_2 have the same length, you only need one loop. This is as efficient (as in speed/performance) as you'll get:

let sum1 = 0, sum2 = 0,
    arr_1 = [3, 5, 22, 5,  7,  2,  45, 75, 89, 21, 2],
    arr_2 = [9, 2, 42, 55, 71, 22, 4,  5,  90, 25, 26];

for (let i = 0; i < arr_1.length; i++) {
    sum1 += arr_1[i], sum2 += arr_2[i];
}

let total = sum1 + sum2;

console.log(`${sum1} + ${sum2} = ${total}`);

Plain for loops are typically faster than more high level looping functions, so you already have the best performing loop possible.

You could also use this for arrays of different lengths by looping the larger one, still only doing one for loop:

let sum1 = 0, sum2 = 0,
    arr_1 = [3, 5, 22, 5,  7,  2,  45, 75, 89, 21, 2, 6, 40, 4],
    arr_2 = [9, 2, 42, 55, 71, 22, 4,  5,  90, 25, 26];

for (let i = 0; i < arr_1.length; i++) {
    sum1 += arr_1[i], sum2 += arr_2[i] || 0;
}

let total = sum1 + sum2;

console.log(`${sum1} + ${sum2} = ${total}`);

When arr_2 runs out, it will start outputting undefined . The arr_2[i] || 0 arr_2[i] || 0 expression will use the secondary value in that case.

An alternative would be to check if the offset exists:

for (let i = 0; i < arr_1.length; i++) {
    sum1 += arr_1[i];
    if(arr_2[i]) sum2 += arr_2[i];
}