JavaScript: Draw a circle

Last update on May 30 2022 09:56:28 (UTC/GMT +8 hours)

JavaScript Drawing: Exercise-2 with Solution

Write a JavaScript program to draw a circle.

Sample output:

Sample Solution:

HTML Code:

<!DOCTYPE html>
  <html>
  <head>
  <meta charset=utf-8 />
  <title>Draw a circle</title>
  </head>
  <body onload="draw();">
  <canvas id="circle" width="150" height="150"></canvas>
  </body>
  </html>

JavaScript Code:

function draw()
  {
var canvas = document.getElementById('circle');
if (canvas.getContext)
{
var ctx = canvas.getContext('2d'); 
var X = canvas.width / 2;
var Y = canvas.height / 2;
var R = 45;
ctx.beginPath();
ctx.arc(X, Y, R, 0, 2 * Math.PI, false);
ctx.lineWidth = 3;
ctx.strokeStyle = '#FF0000';
ctx.stroke();
}
}

Live Demo:

See the Pen javascript-drawing-exercise-2 by w3resource (@w3resource) on CodePen.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04