how to do dual arrray in java javascript code example

Example 1: js array two dimensional

// declaration of a two-dimensional array
// 5 is the number of rows and 4 is the number of columns.
const matrix = new Array(5).fill(0).map(() => new Array(4).fill(0));

console.log(matrix[0][0]); // 0

Example 2: how to read 2 dimensional array in javascript

activities.forEach((activity) => {
    activity.forEach((data) => {
        console.log(data);
    });
});