jQuery equivalent of getting the context of a Canvas

Question

I have the following working code:

ctx = document.getElementById(\"canvas\").getContext(\'2d\');

Is there any way to re-write it to use

Answer 1

The script works before it finds "canvas"

 $(document).ready(function() {
   ctx = $("#canvas");
});

Answer 2

Try:

$("#canvas")[0].getContext('2d');

jQuery exposes the actual DOM element in numeric indexes, where you can perform normal JavaScript/DOM functions.

Answer 3

I have also seen that it's often preferred to use .get(0) to reference a jquery target as HTML element:

var myCanvasElem = $("#canvas").get(0);

Perhaps to help avoid any potential null object references since jquery returns null as an object but working with the element from .get(0) may not fail so silently... You can easily check if the canvas was found first before .get(0) like

if( $("#canvas").length ) ctx = $("#canvas").get(0).getContext('2d');
else console.log('Error: Canvas not found with selector #canvas');

Answer 4

try{ 
   ctx = $('#canvas').get(0).getContext('2d');
}catch(e){ 
    console.log('We have encountered an error: ' + e);
}

or...

if( typeof $('#canvas') === 'undefined'){ 
    var canvas = '<canvas id="canvas"><\/canvas>';
    $('body').append(canvas);
}
setTimeout( function(){ ctx = $('#canvas').get(0).getContext('2d'); }, 500);

Using setTimeout is an easy way to ensure you don't try calling the canvas element before it's fully created and registered to the DOM.