Multiple for-of loops, in the same statement(Javascript)

Question

From mozillas js docs:

for (variable of iterable) {
    statement
 }

This is the standard for of statement in js and I want to do something like this:

for (variable of iterable && variable of iterable) {
   statement
}

I just need the loops to not iterate and then iterate again for each nested for of loop. So something that is similar would be great for my needs but the above seems preferable.

I have 2 arrays that I am trying to iterate through and would like to create objects and check for their equality(or something else) further down.

Example scenario:

for (variable1 of iterable1 && variable2 of iterable2) {
   //code
  if (variable1 === variable2){
   //do something
  }
}

my code:

 if (_.intersection(selections[i],questions[i].correctAnswer)) {
       for (const selection of selections[i]) for (const answer of questions[i].correctAnswer) for(const item of questions[i].qPoints) {
          if (selection === answer){

        numCorrect += item;

        console.log(numCorrect)
              }
            }
          }
        }

Basically what I am doing with intersection is checking if the two arrays intersect using underscoreJS. After that, I am trying to create objects for each of these arrays. Firstly, to check whether or not arrays are equal at any point, and if so incrementing numCorrect by the value of the correctanswer at that index(qPoints). The issue is with nested for loops, I am getting the value of qPoints by some multiple(due to excessive iterations).

What? Are you trying to compare the nth element of iterable1 with every element in iterable2, or just the nth of iterable1 with the nth of iterable2? — James
– James, Commented Nov 9, 2017 at 23:40
If you are working with arrays then forEach or map might be more suited to your needs e.g. iterable1.forEach( function (itemFrom1, i) { var itemFrom2 = iterable2[i]}) — John
– John, Commented Nov 9, 2017 at 23:50

Kevin Kenny · Accepted Answer · 2017-11-09 23:43:18Z

2

You don't have to use 'for' - you can access the underlying Iterator directly.

i1 = iterable1.iterator; i2 = iterable2.iterator;
while (!i1.done && !i2.done) {
    variable1 = i1.next; variable2 = i2.next;

    ... do something with the pair
}

answered Nov 9, 2017 at 23:43

Kevin Kenny

1565 bronze badges

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

Comments

deb2fast · Accepted Answer · 2017-11-10 00:36:46Z

1

Why not just edit your code to be =>

let correctAnswer = questions[i].correctAnswer; 

let qPoints = questions[i].qPoints;

if (_.intersection(selections[i],questions[i].correctAnswer)) {
   selections[i].forEach((selection, index) => {
     if (selection === correctAnswer[index]) {
       numCorrect += qPoints[index];
      }
     }
    }

edited Nov 10, 2017 at 0:36

answered Nov 10, 2017 at 0:08

deb2fast

1,01013 silver badges18 bronze badges

Comments

Sagiv b.g · Accepted Answer · 2017-11-09 23:59:59Z

1

I'm not sure what kind of object or shape you got but if your objects are arrays for example, then just loop over one of them and compare by its index to the other array.

const arr1 = [1,2,3,4,5,10,25,45];
const arr2 = [3,5,8,7,5,10,25,84,98,71,1];

arr1.forEach((o,i) => {
  console.log(o,arr2[i],o == arr2[i]);
});

edited Nov 9, 2017 at 23:59

answered Nov 9, 2017 at 23:46

Sagiv b.g

31.1k10 gold badges72 silver badges106 bronze badges

Comments

bryan60 · Accepted Answer · 2017-11-10 01:35:35Z

0

why does something like this not work:

for (var x = 0; x < selections.length && x < questions.length; x++) {
    var selection = selections[x];
    var question = questions[x];
    if (selection === question.correctAnswer) {
        numCorrect += question.qPoints;
    }
}

answered Nov 10, 2017 at 1:35

bryan60

29.4k5 gold badges56 silver badges71 bronze badges

Collectives™ on Stack Overflow

Multiple for-of loops, in the same statement(Javascript)

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related