jQuery array multiplication

Question

I have two different arrays. I want sum of arrays by multiplying with each element with another array. For example:

function get_total() {
    var i = 0;
    var arr = [];
    var gift_val_len = $('.gift_value').length;
    $('.gift_value').each(function() {
        arr[i++]= parseFloat($(this).val());  // Or this.innerHTML, this.innerText
    });
    var j = 0;
    var arr1 = [];
    $('.gift_number').each(function() {
        arr1[j++]= parseFloat($(this).val());  // Or this.innerHTML, this.innerText
    });
}

Now there are two different arrays like arr1=[15, 20, 25], arr2=[1, 3, 5] and I want result like ((15*1) + (20*3) + (25*5)). How can we achieve this?

Do arrays have the same length always ?

MysterX
– MysterX

2016-05-18 12:21:27 +00:00
Commented May 18, 2016 at 12:21 — MysterX
– MysterX, Commented May 18, 2016 at 12:21
yes.. both array will have same length always..

Himanshu Upadhyay
– Himanshu Upadhyay

2016-05-18 12:23:04 +00:00
Commented May 18, 2016 at 12:23 — Himanshu Upadhyay
– Himanshu Upadhyay, Commented May 18, 2016 at 12:23

score 2 · Accepted Answer · 2016-05-18 12:46:20Z

2

You can do this with a single line with pure JavaScript (no jQuery), using the built-in .map() method:

var arr1=[15, 20, 25], arr2=[1, 3, 5];
var sum = 0;
var arr3 = arr1.map(function(x, index) {
  var curMult = x * arr2[index];
  sum += curMult;
  return curMult;
});
console.log(arr1);
console.log(arr2);
console.log(arr3);
console.log(sum);

This will also sum the elements, as mentioned in the question.

Note: the arrays must be of the same length, otherwise the code will crash.

edited May 18, 2016 at 12:46

answered May 18, 2016 at 12:31

user447356

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4 Comments

Chintan Over a year ago

The question says sum, so maybe add .reduce(function(a, b) { return a+b;}, 0); ?

Deshiknaves Over a year ago

What I was just going to write. You can make it a bit more defensive by: arr1.map(function(x, i) { return x * arr2[i] || x * 1; }); If there is any chance the array might not have the same number of elements.

user447356 Over a year ago

@Chintan thanks,but since it's already iterating the array, no need for another loop. Edited the answer to add sum.

user447356 Over a year ago

@Deshiknaves valid concern, but IMO it's OK to demand arrays of same length. Many built-in methods also throw errors or crash with invalid input.

Hulke · Accepted Answer · 2016-05-18 12:25:35Z

1

Try This:

Inside get_total function, dispatch the function mulitply below with arr1,arr2 params.
Or assign it to a variable, like var mult = multiply(arr1,arr2);

function multiply(arr1, arr2) {
  var res = [];
  for (var i = 0; i < arr1.length; i++) {
    res.push(arr1[i] * arr2[i]);
  };
  return res
};

answered May 18, 2016 at 12:25

Hulke

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Comments

Vladu Ionut · Accepted Answer · 2016-05-18 12:38:21Z

0

To reduce an array to a single value you can use Array Reduce

// Code goes here

var arr1=[15, 20, 25], arr2=[1, 3, 5];


var result = arr1.reduce(function(previousValue, currentValue, currentIndex) {
  var computedValue = currentValue * arr2[currentIndex];
  return previousValue + computedValue;
});
document.write(result);
console.log(result);

answered May 18, 2016 at 12:38

Vladu Ionut

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Comments

JacobS · Accepted Answer · 2016-05-18 12:39:25Z

0

Array.protototype.reduce() might be a good way to handle this.

function multiplyArrays (array1, array2) {
    return array1.reduce(function(prev, curr, i) {
      return prev + (curr * array2[i]);
    }, 0);
}

answered May 18, 2016 at 12:39

JacobS

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