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

If you want to be able access the matrix like so matrix[i][j]

I find it the most convinient to init it in a loop.

var matrix = [],
    cols = 3;

//init the grid matrix
for ( var i = 0; i < cols; i++ ) {
    matrix[i] = []; 
}

this will give you [ [], [], [] ]

so matrix[0][0] matrix[1][0] return undefined and not the error "Uncaught TypeError: Cannot set property '0' of undefined"