I am trying to draw a rectangle on a container using JavaScript, however I keep encountering the below error:

canvas.getContext is not a function

Please see the JavaScript I am using:

console.log("START");

var canvas = document.getElementById($parameters.Id);

console.log(canvas);

var ctx = canvas.getContext("2d");

console.log(ctx);

ctx.fillStyle = "#FF0000";

ctx.fillRect(0, 0, 150, 75);

console.log("END");

I pass in the container id, which from the log I can see is passed successfully. Has anyone got a suggestion as to where I have gone wrong in the code?