How to access 2D array using single for loop in JavaScript?

Question

I have a 2D array which has 10 rows and 10 columns and I want to access a column's element from each row like this:

myArray[0][9]
myArray[1][4]
myArray[2][5]
myArray[3][9]
myArray[4][5]
myArray[5][9]
myArray[6][8]
myArray[7][9]
myArray[8][7];  
myArray[9][8]

The code that I have used:

for(var i=0; i<theatregoers.length; i++)
    {
       myArray[i][9].position=true;
      
       
    }

Note: I do not have any idea how to change column numbers like this each time when loop run. I do not want to use the nest loop, just using a single loop.

@tdranv thanks for ur response, actually I want to access column of each arrow according to the pattern that I mentioned above. — user3718511
– user3718511, Commented Aug 5, 2020 at 6:49
@Jerome myArray[0][9] myArray[1][4] myArray[2][5] myArray[3][9] myArray[4][5] myArray[5][9] myArray[6][8] myArray[7][9] myArray[8][7] myArray[9][8] — user3718511
– user3718511, Commented Aug 5, 2020 at 6:51
is there a particular pattern you want in calling the column number or it could be just random? — Karl L
– Karl L, Commented Aug 5, 2020 at 6:52

Karl L · Accepted Answer · 2020-08-05 07:22:05Z

5

You can do something like this. put the column indexes/number in an array like:

  let colArray = [9,4,5,9,5,9,8,9,7,8] 
    
  for(var i=0; i<myArray.length; i++){  
        myArray[i][colArray[i]].position=true;              
     }

edited Aug 5, 2020 at 7:22

answered Aug 5, 2020 at 6:55

Karl L

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Comments

catcon · Accepted Answer · 2020-08-05 06:54:05Z

2

You can loop your array like this

var row = 10;
var column = 10;

for (var i = 0; i < row * column; i++) {
     myArray[Math.floor(i / row)][i % column].position = true;
}

edited Aug 5, 2020 at 6:54

answered Aug 5, 2020 at 6:49

catcon

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2 Comments

Avius Over a year ago

The OP asked for an arbitrary pattern for the second index, so this answer is incorrect.

catcon Over a year ago

@Avius: agree, OP added more info later in the comment

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