JavaScript: Calculate the area and perimeter of a circle

JavaScript Object: Exercise-9 with Solution

Circle Area & Perimeter

Write a JavaScript program to calculate circle area and perimeter.
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.

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

Sample Solution:

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));

Output:

Area = 28.27
VM1407:17 perimeter = 18.85

Flowchart:

Live Demo:

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

For more Practice: Solve these Related Problems:

• Write a JavaScript class that calculates both the area and circumference of a circle given its radius.
• Write a JavaScript function that prompts the user for the radius and then displays the computed area and perimeter.
• Write a JavaScript function that validates the radius input to ensure it is a positive number before calculations.
• Write a JavaScript function that compares the area of a circle to that of a square with an equivalent perimeter.

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