[Old Pedant]

What the heck...

var cellWidth = 25;
var cellHeight = 25;

var grass=new Image();
var cement=new Image();
grass.src="new/grass.png";
grass.width = cellWidth; grass.height = cellHeight;
cement.src="new/cement.jpg";
cement.width = cellWidth; cement.height = cellHeight;

for( row=0; row < map.length; ++row)
{
    var line = map[row];
    for( column=0; column < line.length; ++column )
    {
	context.drawImage( line[column] == "1" ? grass : cement,
                           column*cellWidth, 
                           row*cellHeight 
        );
    }
}

That's actually getting readable.