This is my HTML code, showing the canvas:

 <canvas id=backgroundCanvas width=550 height=600></canvas>

 <canvas id=playerCanvas width=550 height=600></canvas

 <canvas id=enemiesCanvas width=550 height=600></canvas>

This is where the problem is said to occur:

game.contextBackground = document.getElementById(backgroundCanvas).getContext(2d); // line 32

game.contextPlayer = document.getElementById(playerCanvas).getContext(2d); // line 33

game.contextEnemies = document.getElementById(enemiesCanvas).getContext(2d); // line 34

the error occurs on line 34 where it says:

Uncaught TypeError: Cannot read property 'getContext' of null

any help is much appreciated :)