adding together each array within forEach loop javascript?

Question

Here is my code;

var data = [[40, 20, 60], [20, 30, 10], [50, 75, 40]];
var averageData = [];
data.forEach(function(entries) {
    entries.reduce(function(a, b) {
        return a + b[1];
    }, 0);
    console.log(entries);
});

I would like to be able to add the numbers from each array together.

But I'm not sure how I can get each array of numbers added together from the forEach loop?

From this data I would like to output instead [120, 60, 165].

It is important that the data is within a nested array, the aim is to try get it out of the nested array onto a single line with the above output.

Hope someone can offer some advice!

Thanks

Rayon · Accepted Answer · 2020-04-03 12:23:20Z

11

Use Array#map instead

Note that b[1] holds nothing(undefined) and entries.reduce returns a reduced value, either return it of keep it in variable

var data = [
  [40, 20, 60],
  [20, 30, 10],
  [50, 75, 40]
];
var averageData = data.map(function(entries) {
  return entries.reduce(function(a, b) {
    return a + b;
  }, 0);
});

console.log(averageData)

Edit- As suggested in comments by @Tushar, ES6 version

var data = [
  [40, 20, 60],
  [20, 30, 10],
  [50, 75, 40]
];
console.log(data.map(arr => arr.reduce((a, b) => a + b, 0)));

edited Apr 3, 2020 at 12:23

answered Jul 6, 2016 at 8:10

Rayon

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1 Comment

Tushar Over a year ago

ES6: data.map(arr => arr.reduce((a, b) => a + b, 0))

Anson · Accepted Answer · 2016-07-06 08:13:19Z

0

reduce() will return the sum as you want at last. See as below.

var data = [[40, 20, 60], [20, 30, 10], [50, 75, 40]];
var averageData = []
data.forEach(function(entries) {

    var sum = entries.reduce(function(a, b) {
      return a + b;
    }, 0)
    console.log(sum)

})

answered Jul 6, 2016 at 8:13

Anson

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Comments

Cédric MARTIN · Accepted Answer · 2016-07-06 08:17:20Z

0

If your values are safe (meaning you know where there come from) you could use eval to quickly sum the values.

var data = [[40, 20, 60], [20, 30, 10], [50, 75, 40]];
var totals = [];

data.forEach(function(a, i) {
  totals.push(eval(a.join('+')));
});

console.log(totals);

Not the most efficient way but it works

answered Jul 6, 2016 at 8:17

Cédric MARTIN

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