CODEWITHSUNDEEP
javascriptarrays
Lazy
Lazy

Reputation: 1837

Sum arrays in javascript

I have these arrays:

// I want to calculate these arrays each other.
var a = [1,2,3]
var b = [1,2,3]
var c = [3,4,5]
// ->
var result = [5, 8, 11]

I can calculate two array with below method but how can I sum n arrays?

Array.prototype.Sum = function (arr) {
    var s = [];
    if (arr != null && this.length == arr.length) {
        for (var i = 0; i < arr.length; i++) {
            var c = this[i] + arr[i]
            s.push(c);
        }
    }
    return s;
}

Upvotes: 0

Views: 169

Answers (4)

Hilder Vitor Lima Pereira
Hilder Vitor Lima Pereira

Reputation: 1690

With this function, you can sum several arrays and you don't need to "encapsulate" your arrays into another array...

Also, it works on old browsers.

function Sum(){
  if (arguments.length == 0){
    return null;
  }
  var s = arguments[0];
  for(var j = 1; j < arguments.length; j++) {
     var arr = arguments[j];
     for (var i = 0; i < arr.length; i++) {
         s[i] = s[i] + arr[i];
     }
  }
  return s;
}

Just call Sum(a, b) or Sum(a, b, c) ...

You can put it in your prototype too if you want (and make little changes to use this if you want to sum in place).

Upvotes: 3

Witiko
Witiko

Reputation: 3387

A plain old ECMAScript 3 solution:

var arrays = [
    [1, 2, 3],
    [1, 2, 3],
    [3, 4, 5]
];

function sum() {
  var sum = [];
  for(var i = 0; i < arguments.length; ++i) {
    for(var j = 0; j < arguments[i].length; ++j)
      sum[j] = (sum[j] || 0) + arguments[i][j];
  } return sum;
}

sum.apply(this, arrays);              // [ 5, 8, 11 ]
sum(arrays[0], arrays[1], arrays[2]); // [ 5, 8, 11 ]

Upvotes: 3

Oriol
Oriol

Reputation: 288120

Assuming

var arrays = [
    [1,2,3],
    [1,2,3],
    [3,4,5]
];

Using your Sum with EcmaScript 5 array methods,

var result = arrays.reduce(function(arr1, arr2){
    return arr1.Sum(arr2);
});

Alternatively, consider not polluting Array.prototype and just using something like (ES5)

var result = arrays.reduce(function(arr1, arr2) {
    return arr1.map(function(num, index){
        return num+arr2[index];
    });
});

Or, simplifying using EcmaScript 6 arrow functions,

var result = arrays.reduce(
    (arr1, arr2) => arr1.map(
        (num, index) => num+arr2[index]
    )
);

Upvotes: 5

Chris Franklin
Chris Franklin

Reputation: 3984

a.sum(b).sum(c);

That should do it.

Upvotes: 0

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