CODEWITHSUNDEEP
javascript
user9703772
user9703772

Reputation:

JS - Sum Of Two Arrays where arrays can be of unequal length

I need function like this.

function sum(arr1, arr2) {
  return totalArray
};

sum([1,2,3,4], [5,6,7,8,9]) // [6,8,10,12,9]

I tried it this way:

var array1 = [1, 2, 3, 4];
var array2 = [5, 6, 7, 8, 100];
var sum = array1.map((num, idx) => num + array2[idx]); // [6,8,10,12]

Upvotes: 2

Views: 1225

Answers (7)

Yosvel Quintero
Yosvel Quintero

Reputation: 19070

First you can get an array out of the function's arguments using Spread syntax (...), then sort it by array's length using Array.prototype.sort() and finally Array.prototype.reduce() to get the result array

Code:

const sum =(...arrays) => arrays
  .sort((a, b) => b.length - a.length)
  .reduce((a, c) => a.map((n, i) => n + (c[i] || 0)) || c)

// two arrays
const resultTwoArrays = sum([1, 2, 3, 4], [5, 6, 7, 8, 9])
console.log(resultTwoArrays) // [6, 8, 10, 12, 9]

// three arrays or more...
const resultThreeArrays = sum([1, 2, 3, 4], [5, 6, 7, 8, 9], [1, 2])
console.log(resultThreeArrays) // [7, 10, 10, 12, 9]
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 4

Mamun
Mamun

Reputation: 68943

Try with map():

function sum(arr1, arr2) {
  var [a1, a2] = arr1.length > arr2.length ? [arr1, arr2] : [arr2, arr1]
  var totalArray = a1.map(function(i, idx){
    i = (i + a2[idx] || i + 0); 
    return i;
  })
  return totalArray;
};

console.log(sum([1,2,3,4], [5,6,7,8,9])) // [6,8,10,12,9]

Upvotes: 0

david
david

Reputation: 18268

Are we code golfing this? Here's a generator solution.

const summer = function*(a, b, i=0) {
  while(i < a.length || i < b.length) yield (a[i] || 0)  + (b[i++] || 0);
};
const sum = (a, b) => [...summer(a,b)];

console.log(sum([1,2,3,4], [5,6,7,8,9])) // [6,8,10,12,9]

Upvotes: 1

T.J. Crowder
T.J. Crowder

Reputation: 1074555

I try this way.

 var array1 = [1, 2, 3, 4];
 var array2 = [5, 6, 7, 8, 100];
 var sum = array1.map((num, idx) => num + array2[idx]); // [6,8,10,12]

Very close, but map will stop at the end of array1, so you won't get the subsequent entries from array2. Just pick the longer of the two arrays, then handle the fact that the other array may not have an entry at arrayX[idx]. You can do that with the || 0 idiom:

function sum(array1, array2) {
  var a, b;
  if (array1.length > array2.length) {
    a = array1;
    b = array2;
  } else {
    a = array2;
    b = array1;
  }
  return a.map((num, idx) => num + (b[idx] || 0));
}

console.log(sum([1, 2, 3, 4], [5, 6, 7, 8, 100]));

Alternately, you can use the new (but polyfill-able) Array.from to create the result array and use the callback to build the entries:

function sum(array1, array2) {
  return Array.from(
    {length: Math.max(array1.length, array2.length)},
    (_, i) => (array1[i] || 0) + (array2[i] || 0)
  );
}

console.log(sum([1, 2, 3, 4], [5, 6, 7, 8, 100]));

Mosho's answer is wonderfully simple, though.

Upvotes: 1

Mosho
Mosho

Reputation: 7078

At the risk of being unpopular due to using a loop:

function sum(arr1, arr2) {
    let totalArray = [];
    const totalLength =  Math.max(arr1.length, arr2.length);
    for (let i = 0; i < totalLength; i++) {
        totalArray[i] = (arr1[i] || 0) + (arr2[i] || 0);
    }
    return totalArray;
}

The || 0 handles the possibility the array doesn't have an entry at i, because if it doesn't, the result of arrX[i] is undefined, and undefined || 0 is 0.

Upvotes: 2

Ori Drori
Ori Drori

Reputation: 192006

Find the long and short array according to length. Iterate the short array with Array.map(), and take the value from the long array. Then add the leftovers from the long array using Array.slice(), and Array.concat():

function sum(arr1, arr2) {
  const [l, s] = arr1.length >= arr2.length ? [arr1, arr2] : [arr2, arr1];
    
  return s.map((n, i) => n + l[i])
        .concat(l.slice(s.length));
};

console.log(sum([1,2,3,4], [5,6,7,8,9]));

Upvotes: 1

Ankit Agarwal
Ankit Agarwal

Reputation: 30739

You can have a custom logic something like this:

function sum(arr1, arr2) {
  var length, selectedArray, nonSelectedArray;
  if(arr1.length>arr2.length){
   length = arr1.length;
   selectedArray = arr2;
   nonSelectedArray = arr1;
  }else {
   length = arr2.length;
   selectedArray = arr1;
   nonSelectedArray = arr2;
  }
  var totalArray = [];
  for(var i=0; i<length; i++){
    if(selectedArray[i]){
      totalArray.push(selectedArray[i] + nonSelectedArray[i]);
    } else {
      totalArray.push(nonSelectedArray[i]);
    }
  }
  return totalArray
};

var res = sum([1,2,3,4], [5,6,7,8,9]);
console.log(res);

Upvotes: 0

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