forEach loop through two arrays at the same time in javascript

Question

I want to build a for loop that iterates through two variables at the same time. n is an array and j goes from 0 to 16.

var n = [1,2,3,5,7,8,9,11,12,13,14,16,17,18,20,21,22];
var m = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16];

m.forEach(k => {
    n.forEach(i => {
        console.log(i, k)
    });
};

The final result should output:

1,0
2,1
3,2
5,3
(...)

Unfortunately this loop doesn't do that for some reason as it repeats every number 17 times.

What am I missing here?

Where is the second array? You currently have one `for` loop and a `forEach` over an array. I'm not sure what the expected outcome is - do you just want to print `0, 1` -> `1, 2`, etc? — VLAZ, Sep 12 '19 at 08:51
Assuming that's the pattern you probably only need one loop. — Andy, Sep 12 '19 at 08:51

CertainPerformance · Accepted Answer · 2019-09-12T08:59:39.603

91

Use the second parameter forEach accepts instead, which will be the current index you're iterating over:

n = [1,2,3,5,7,8,9,11,12,13,14,16,17,18,20,21,22];

n.forEach((element, index) => {
  console.log(element, index);
});

If you have two separate arrays to begin with, in each iteration, access the [index] property of the other array:

var n = [1, 2, 3, 5, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 20, 21, 22];
var m = [0, 1, 2, 3, 4, 5, 6, 7,  8,  9,  10, 11, 12, 13, 14, 15, 16];

n.forEach((num1, index) => {
  const num2 = m[index];
  console.log(num1, num2);
});

edited Sep 12 '19 at 08:59

answered Sep 12 '19 at 08:51

CertainPerformance

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2

That works indeed. Now imagine that instead of the index I wanted a specific array. I've edited the post to reflect that. – FilipeTeixeira Sep 12 '19 at 08:57
nice way to handle this – Mariusz Oct 18 '22 at 18:47

forEach loop through two arrays at the same time in javascript

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