How to use reduce() instead a traditional foreach loop with ReactJs app

Question

I have the following code on my React app:

var numberOfAnswers = 0
var sumOfAnswers = 0

respostas.forEach(function (element,index) {
    console.log(index+"-"+element["responses"])
    numberOfAnswers += element["responses"]
    sumOfAnswers += (index*element["responses"])                
})

it works perfectly, but I want to use something like that:

const arrSum = respostas => respostas.reduce((a,b) => a + b, 0)

Is it possible to do that using reduce() and if it is possible, how can I do that?

Dmitry Reutov · Accepted Answer · 2019-10-16 22:12:06Z

1

sure, it is possible

const [numberOfAnswers, sumOfAnswers] = respostas.reduce((res, element, index) => 
  [
    res[0] + element.responses, 
    res[1] + index * element.responses
  ] , [0, 0])

answered Oct 16, 2019 at 22:12

Dmitry Reutov

3,0321 gold badge9 silver badges22 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Cat_Enthusiast · Accepted Answer · 2019-10-16 22:13:14Z

With reduce, you can instantiate your variables by having them as a default object (see 2nd argument), then populate that object as you iterate over the array. The first argument of reduce accepts a callback function, in which that function accepts 3 arguments, the total object, current item being iterated over and its index. On each iteration, you populate that object and return it so the next iteration has access to the updated data.

Try something like this:

let data = repostas.reduce((object, current, index) => {
   object.numberOfAnswers += current["responses"]
   object.sumOfAnswers += (index * current["responses"])
   return object
}, { numberOfAnswers: 0, sumOfAnswers: 0})

Then you can just access your points via the data object.

Collectives™ on Stack Overflow

How to use reduce() instead a traditional foreach loop with ReactJs app

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related