1// declaration of a two-dimensional array
2// 5 is the number of rows and 4 is the number of columns.
3const matrix = new Array(5).fill(0).map(() => new Array(4).fill(0));
4
5console.log(matrix[0][0]); // 0
6

1let x = [
2  [1, 2, 3],
3  [4, 5, 6],
4  [7, 8, 9]
5];
6console.log(items[0][0]); // 1
7console.log(items[0][1]); // 2
8console.log(items[1][0]); // 4
9console.log(items[1][1]); // 5
10console.log(items);

1
2        
3            
4        
5     activities.forEach((activity) => {
6    activity.forEach((data) => {
7        console.log(data);
8    });
9});

1var items =[
2     
3  [1,        2,       3],//this is row 0
4  [4,        5,       6],//this is row 1
5  [7,        8,       9] //this is row 2
6//cullom 0   cullom 1   cullom2
7  
8]
9
10console.log(/* variable name */ items[/*row*/ 0][/*cullom*/ 0]);

1/*having the previous array easy to make is very useful*/
2
3function Array2D(x, y){
4 let arr = Array(x);
5  for(let i = 0; i < y; i++){
6   arr[i] = Array(y);
7  }
8  return arr;
9}
10
11function Array3D(x, y, z){
12 let arr = Array2D(x, y);
13      for(let i = 0; i < y; i++){
14       for(let j = 0; j < z; j++){
15        arr[i][j] = Array(z);
16       }
17      }
18  return arr;
19}
20
21function Array4D(x, y, z, w){
22 let arr = Array3D(x, y, z);
23      for(let i = 0; i < x; i++){
24       for(let j = 0; j < y; j++){
25        for(let n = 0; n < z; n++){
26        arr[i][j][n] = Array(w);
27       }
28       }
29      }
30  return arr;
31}
32/*making the array*/
33let myArray = Array4D(10, 10, 10, 10);

1var x = new Array(10);
2
3for (var i = 0; i < x.length; i++) {
4  x[i] = new Array(3);
5}
6
7console.log(x);