jQuery’s equivalent of getting a Canvas’s context

Problem

I’ve got the following code that works:

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

Is it possible to rewrite it to utilize $? If you do this, you will fail:

ctx = $("#canvas").getContext('2d');

Asked by Claudiu

Solution #1

Try:

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

The real DOM element is exposed in numeric indexes by jQuery, where you can perform standard JavaScript/DOM functions.

Answered by Matt

Solution #2

I’ve also seen that is frequently preferred. To refer to a jquery target as an HTML element, use get(0):

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

Because jquery returns null as an object when working with the element from, this could be to help eliminate any potential null object references. It’s possible that get(0) won’t fail so quietly… You can quickly see if the canvas was discovered first. like get(0)

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

Answered by OG Sean

Solution #3

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);

SetTimeout is a simple approach to ensure that you don’t try to call the canvas element before it has been fully formed and registered to the DOM.

Answered by MistyDawn

Solution #4

Before it finds “canvas,” the script works.

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

Answered by александр лобазов

Post is based on https://stackoverflow.com/questions/2925130/jquery-equivalent-of-getting-the-context-of-a-canvas