Declare an empty two-dimensional array in Javascript?

Question

I want to create a two dimensional array in Javascript where I\'m going to store coordinates (x,y). I don\'t know yet how many pairs of coordinates I will have because they

Answer 1

var arr = [];
var rows = 3;
var columns = 2;

for (var i = 0; i < rows; i++) {
    arr.push([]); // creates arrays in arr
}
console.log('elements of arr are arrays:');
console.log(arr);

for (var i = 0; i < rows; i++) {
    for (var j = 0; j < columns; j++) {
        arr[i][j] = null; // empty 2D array: it doesn't make much sense to do this
    }
}
console.log();
console.log('empty 2D array:');
console.log(arr);

for (var i = 0; i < rows; i++) {
    for (var j = 0; j < columns; j++) {
        arr[i][j] = columns * i + j + 1;
    }
}
console.log();
console.log('2D array filled with values:');
console.log(arr);