forEach loop through two arrays at the same time in javascript

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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);
});

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FilipeTeixeira
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FilipeTeixeira

Architect, Neurobiologist and now adventuring through the oceans of data analysis. Started with R and I can't let it go.

Updated on September 12, 2020

Comments

  • FilipeTeixeira
    FilipeTeixeira over 3 years

    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?