Typescript - multidimensional array initialization

Question

I\'m playing with Typescript and I wonder, how to properly instantiate and declare multidimensional array. Here\'s my code:

class Something {
    private thi         


        

Answer 1

Here is an example of initializing a boolean[][]:

const n = 8; // or some dynamic value
const palindrome: boolean[][] = new Array(n)
                                   .fill(false)
                                   .map(() => new Array(n)
                                   .fill(false));

Answer 2

If you want to do it typed:

class Something {

  areas: Area[][];

  constructor() {
    this.areas = new Array<Array<Area>>();
    for (let y = 0; y <= 100; y++) {
      let row:Area[]  = new Array<Area>();      
      for (let x = 0; x <=100; x++){
        row.push(new Area(x, y));
      }
      this.areas.push(row);
    }
  }
}

Answer 3

You only need [] to instantiate an array - this is true regardless of its type. The fact that the array is of an array type is immaterial.

The same thing applies at the first level in your loop. It is merely an array and [] is a new empty array - job done.

As for the second level, if Thing is a class then new Thing() will be just fine. Otherwise, depending on the type, you may need a factory function or other expression to create one.

class Something {
    private things: Thing[][];

    constructor() {
        this.things = [];

        for(var i: number = 0; i < 10; i++) {
            this.things[i] = [];
            for(var j: number = 0; j< 10; j++) {
                this.things[i][j] = new Thing();
            }
        }
    }
}

Answer 4

You can do the following (which I find trivial, but its actually correct). For anyone trying to find how to initialize a two-dimensional array in TypeScript (like myself).

Let's assume that you want to initialize a two-dimensional array, of any type. You can do the following

const myArray: any[][] = [];

And later, when you want to populate it, you can do the following:

myArray.push([<your value goes here>]);

A short example of the above can be the following:

const myArray: string[][] = [];
myArray.push(["value1", "value2"]);

Answer 5

Beware of the use of push method, if you don't use indexes, it won't work!

var main2dArray: Things[][] = []

main2dArray.push(someTmp1dArray)
main2dArray.push(someOtherTmp1dArray)

gives only a 1 line array!

use

main2dArray[0] = someTmp1dArray
main2dArray[1] = someOtherTmp1dArray

to get your 2d array working!!!

Other beware! foreach doesn't seem to work with 2d arrays!