How to add value and duplicate item in multidimensionnel array?

Question

I've got a multidimensionnal array like

var a = [['Dog','Cat'],[1,2]];

My goal is to get an array like

var b = [['G','X','G','X'], ['Dog','Dog', 'Cat', 'Cat'],[1,1,2,2]];

For this i'm using a loop but i didn't get the result i need.

for (i=0;i<a.length;i++){ for (j=0;j<a[i].length;j++){ b[0][j] = 'G'; b[1][j] = a[i][j]; b[0][j] = 'X'; b[1][j] = a[i][j]; } }

I try to insert the value of a array to b array but i need to duplicate each value and insert a 'G' next a 'X'

It should be (not sure it is correct)

b[] = ['G'],[a[0][0]],[a[1][0]] b[] = ['X'],[a[0][0]],[a[1][0]] b[] = ['G'],[a[0][1]],[a[1][1]] b[] = ['X'],[a[0][1]],[a[1][1]]

What's the process to get from your first array to your second? If you describe all the steps/requirements it will be considerably easier for people to help. — DBS
– DBS, Commented Oct 19, 2022 at 9:15
can you change this requirement at all or are you stuck with it. — chovy
– chovy, Commented Oct 19, 2022 at 9:33
Will the child arrays always contain the same number of elements? — Rory McCrossan
– Rory McCrossan, Commented Oct 19, 2022 at 9:35
I can change. The idea is to get an array with the G and X value. — Chris
– Chris, Commented Oct 19, 2022 at 9:36

RowBlaBla · Accepted Answer · 2022-10-19 09:37:39Z

If I did understand you correct and you need to duplicate your data in array a and alternate 'G' and 'X' in your target array b, then you could do something like that:

var a = [['Dog','Cat'],[1,2]]; var b = [[],[],[]]; for (i = 0; i < a[0].length; ++i){ for (j = 0; j < 2; ++j) { b[0][i * 2 + j] = j === 0 ? 'G' : 'X'; b[1][i * 2 + j] = a[0][i]; b[2][i * 2 + j] = a[1][i]; } }

Portevent · Accepted Answer · 2022-10-19 09:50:24Z

In order to solve that problem easly, I'll break it down in two part. First is duplicating the line, and then inserting the GXGXGXGX...

Step 1 : duplicate the lines

Answered here : How to duplicate elements in a js array?

function duplicate(item){ return [item, item] } var a = [['Dog','Cat'],[1,2]]; // For each list inside a, duplicate the element of that sublist var b = a.map(sublistOfNumberOrPet => sublistOfNumberOrPet .flatMap(duplicate)) // b = [['Dog','Dog', 'Cat', 'Cat'],[1,1,2,2]]

Step 2 : Add G X G X...

We will build a list of G, X, G, X to append to b

b = [['Dog','Dog', 'Cat', 'Cat'],[1,1,2,2]] // Create a new array, the same length as the first element of b // And fill it with `G` and `X` (if index is odd : `G`, else `X`) gxgx = Array.from({length: b[0].length}, (x, index) => index%2?'G':'X'); // Append our gxgx inside `b (unshift add it in the first place) b.unshift(gxgx)

More informations about unshift

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How to add value and duplicate item in multidimensionnel array?

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Step 1 : duplicate the lines

Step 2 : Add G X G X...

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Step 1 : duplicate the lines

Step 2 : Add G X G X...

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