sanity check to get the context if input happens to be the canvas; errors if it can't return a context
Download node at nodejs.org and install it, if you haven't already.
npm install force-canvas-context --save
var forceCanvasContext = require('force-canvas-context');
let canvas = document.createElement('canvas')
let context = forceCanvasContext(canvas)
context = forceCanvasContext(canvas.getContext('2d'))
context = forceCanvasContext('not a context or canvas') // Error
forceCanvasContext(ctx:context):context
...
MIT