JavaScript: Calculate the area and perimeter of a circle

Last update on May 30 2022 10:02:03 (UTC/GMT +8 hours)

JavaScript Object: Exercise-9 with Solution

Write a JavaScript program to calculate the area and perimeter of a circle. Create two methods to calculate the area and perimeter. The radius of the circle will be supplied by the user.

JavaScript: Area and circumference of a circle

In geometry, the area enclosed by a circle of radius r is πr2. Here the Greek letter π represents a constant, approximately equal to 3.14159, which is equal to the ratio of the circumference of any circle to its diameter.

The circumference of a circle is the linear distance around its edge.

Javascript:area and perimeter of a circle

Why is the area of a circle of a circle pi times the square of the radius?

Sample Solution: -

HTML Code:

<!DOCTYPE html>
  <html>
  <head>
  <meta charset="utf-8">
  <title>Area and Perimeter of a circle</title>
  </head>
  <body>
</body>
  </html>

JavaScript Code:

function circle(radius)
{
    this.radius = radius;
  // area method
    this.area = function () 
    {
        return Math.PI * this.radius * this.radius;
    };
  // perimeter method
    this.perimeter = function ()
    {
        return 2*Math.PI*this.radius;
    };
}
var c = new circle(3);
console.log('Area =', c.area().toFixed(2));
console.log('perimeter =', c.perimeter().toFixed(2));

Sample Output:

Area = 28.27
VM1407:17 perimeter = 18.85

Flowchart:

Live Demo:

See the Pen javascript-object-exercise-9 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

Previous: Write a JavaScript program to create a Clock.
Next: Write a JavaScript program to sort an array of JavaScript objects.

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