# JavaScript practice: Find out the area and perimeter of a circle :

This is a JavaScript practice problem. We will learn how to find the area and perimeter of a circle in JavaScript. We will use one class to solve this problem.
With this program, you will get familiar with *JavaScript class* and *object*, JavaScript *Math* class and how to use constants of *Math* class in a JavaScript program.

## Algorithm :

We need only the *radius* to calculate both *area* and *perimeter* of a circle.

```
Perimeter = 2 * π * radius
Area = π * radius * radius
```

So, we need *π* and *radius* to calculate both. *π* is a constant. We can store it in a variable or we can use its value from JavaScript *Math* module. In this example, we will use the *Math* module. We will use one class to hold the value of *radius* and the methods to do these calculations.

## JavaScript program :

```
class Circle {
constructor(r) {
this.radius = r;
}
getArea() {
return(Math.PI * Math.pow(this.radius, 2)).toFixed(2);
}
getPerimeter() {
return (2 * Math.PI * this.radius).toFixed(2);
}
}
let radius = 10;
let circle = new Circle(radius);
console.log(`Area for radius ${radius} is ${circle.getArea()}`);
console.log(`Perimeter for radius ${radius} is ${circle.getPerimeter()}`);
```

### Explanation :

*Circle*class is used to hold the value of the*radius*. It has one constructor. It takes the radius as an argument and assigns it to the local variable*radius*.- This class also has two methods
*getArea()*and*getPerimeter()*to get the area and perimeter of a circle for the current*radius*.*toFixed(2)*is used to change the calculated value to two decimal places. - In this example, we are creating one variable
*radius*(this is a different variable) with value*10*. - We are creating one
*Circle*object by passing the value of*radius*to its constructor. - Finally, we are printing the area and perimeter of the circle.

It will print the below output :

```
Area for radius 10 is 314.16
Perimeter for radius 10 is 62.83
```

Try to run the example with a different values of *radius* and drop a comment below if you have any queries.