How do I put a multidimensional array in object constructor Javascript

Question

I have a constructor:

function a(x, y){\n
    this.array[x][y];
     for(var i = 0; i<x; i++){
         for(var j = 0l j<y; j++){
             this.array[i][j]=0;
         }
     }
}

How would I declare this.array correctly? (this.array is supposed to be a multidimensional array.

not sure what this.array[x][y]; is supposed to do? can you elaborate — zfrisch
– zfrisch, Commented Mar 5, 2018 at 20:09
The first thing you need to remember about Javascript, there isn't really such a thing as a multidimensional array. But you can have arrays that contain arrays, once you work out what that means, implementing a type of multidimensional array of X dimensions is possible. — Keith
– Keith, Commented Mar 5, 2018 at 20:10
this.array = Array.from({length: x}, () => Array(y).fill(0)) — Thomas
– Thomas, Commented Mar 5, 2018 at 20:13

Ele · Accepted Answer · 2018-03-05 20:21:54Z

1

If you want to initialize that array, use this approach:

                         +---- Length for outter array
                         |
                         v
this.array = Array.from({length: x}, () => Array(y).fill(0));
                                                ^
                                                |
                                                +--- This will initialize the nested arrays

function a(x, y){
  this.array = Array.from({length: x}, () => Array(y).fill(0));
  console.log(JSON.stringify(this.array, null, 2))
}

a(2, 3);

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Mar 5, 2018 at 20:21

answered Mar 5, 2018 at 20:13

Ele

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1 Comment

Thomas Over a year ago

the other way around, Array.from({length: x}, () => Array(y).fill(0)). check what happens with your code if you change this.array[0][0]=1; all columns are changed, as they all reference the same sub-array

Pac0 · Accepted Answer · 2018-03-05 20:13:38Z

a multidimensional array is an array of arrays

just declare an array, then fill it with the x arrays inside, each with y elements.

To keep the same style as your provided code, you can do something like this

    function a(x, y){
         var myArray = [];
         for(var i = 0; i < x; i++){
             myArray[i] = [];
             for(var j = 0; j < y; j++){
                 myArray[i][j] = 0;
             }
         }
         return myArray;
    }

    var exampleArray = a(3,4);
    console.log(exampleArray);

I wrote it like your snippet of code for understanding. However, there are better ways ('clearer' and probably more efficient, and more 'javascriptish') to write arrays. For example, see Ele's answer.

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