How to draw a circle in HTML5 Canvas using JavaScript?

Question

How to draw a simple circle in HTML5 Canvas using minimum JavaScript code?

Answer 1

Creating shapes is easier using new Canvas Path2D, which uses the same canvas drawing API, and allow separation of the declaration from drawing itself, and reuse of complex geometry:

var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
var centerX = canvas.width / 2;
var centerY = canvas.height / 2;
var radius = 70;

let circle = new Path2D();  // <<< Declaration
circle.arc(centerX, centerY, radius, 0, 2 * Math.PI, false);

context.fillStyle = 'blue';
context.fill(circle); //   <<< pass circle to context

context.lineWidth = 10;
context.strokeStyle = '#000066';
context.stroke(circle);  // <<< pass circle here too

body {
margin: 0px;
padding: 0px;
}

<canvas id="myCanvas" width="578" height="200"></canvas>

Answer 2

Here is how to draw a circle using JavaScript in HTML5:

const canvas = document.getElementById('myCanvas');
const context = canvas.getContext('2d');
const centerX = canvas.width / 2;
const centerY = canvas.height / 2;
const radius = 70;

context.beginPath();
context.arc(centerX, centerY, radius, 0, 2 * Math.PI, false);
context.fillStyle = 'green';
context.fill();
context.lineWidth = 5;
context.strokeStyle = '#003300';
context.stroke();

body {
  margin: 0px;
  padding: 0px;
}

<canvas id="myCanvas" width="578" height="200"></canvas>

Answer 3

First of all, you need to get the canvas context:-

const canvas = document.querySelector('#canvas');
const ctx = canvas.getContext('2d');

Now let us define the position and radius:-

const X = canvas.width / 2;
const Y = canvas.height / 2;
const radius = 45;

Now let us set the color and line width:-

ctx.lineWidth = 3;
ctx.strokeStyle = '#FF0000';

Now, to draw the circle, we have to use the arc method and set the angle to 2 X π

ctx.beginPath();
ctx.arc(X, Y, radius, 0, 2 * Math.PI, false);
ctx.stroke();