How to find the area of ​​a circle using javascript

A circle is a basic shape in two-dimensional geometry. It has a very important attribute - its area. The formula for the area of ​​a circle is S=πr² (where S represents the area of ​​the circle, π represents pi, and r represents the radius of the circle).

In programming, JavaScript can be used to calculate the area of ​​a circle. This article will show you how to find the area of ​​a circle in JavaScript.

1. Pure handwriting

First of all, we can implement this function by handwriting code.

In JavaScript, we can use the constants and functions provided by the Math object to calculate the area of ​​a circle. We can achieve this through the following code:

// 计算圆面积的函数
function circleArea(radius) {
  let area = Math.PI * (radius ** 2);
  return area;
}

// 调用函数，计算半径为 5 的圆的面积
let radius = 5;
let area = circleArea(radius);
console.log(area);

In the above code, we define a function named circleArea and pass in the radius of the circle. In the function, we use Math.PI and the exponent operator ** to calculate the area of ​​the circle and assign the result to the area variable. Finally, we use the return statement to return the result of the calculation to the code that called it.

The code output result is 78.53981633974483, which is in line with our expectations.

2. Encapsulate into an object

In addition to using functions, we can also encapsulate this method of calculating the area of ​​a circle into an object and directly call methods on the object elsewhere. .

The following is a sample code:

// 封装计算圆面积的方法，将其作为 circle 对象的方法
let circle = {
  // 属性：圆周率
  PI: Math.PI,

  // 方法：计算圆面积
  area: function (radius) {
    return this.PI * (radius ** 2);
  }
}

// 调用 circle 对象的方法，计算半径为 5 的圆的面积
let radius = 5;
let area = circle.area(radius);
console.log(area);

In the above code, we use objects and methods to encapsulate the method of calculating the area of ​​a circle. In the circle object, we define a area method, pass in the radius, calculate the area of ​​the circle, and return the calculation result. We use the object to call the area method in the code to calculate the area of ​​the circle. The code output is the same as the previous code.

3. Use classes to encapsulate

In the idea of ​​object-oriented programming, we can use classes to encapsulate the properties and methods of objects for higher-level encapsulation.

The following is a sample code that uses an ES6 class to encapsulate a method for calculating the area of ​​a circle:

// 定义一个名为 Circle 的类
class Circle {
  // 构造函数，圆周率作为类的静态属性
  static PI = Math.PI;
  constructor(radius) {
    this.radius = radius;
  }

  // 计算圆的面积
  area() {
    return Circle.PI * (this.radius ** 2);
  }
}

// 创建一个 Circle 对象，并调用其方法 area 计算圆的面积
let radius = 5;
let circle = new Circle(radius);
let area = circle.area();
console.log(area);

In this sample code, we created a class named Circle , the constructor constructor is defined in the class, and pi Math.PI is used as a static property of the class. There is also a area method in the class, which can be used to calculate the area of ​​a circle. This method is called in the code to calculate the area of ​​a circle with a radius of 5. The code output is the same as the previous code.

Summary

Through the above three sample codes, we can find that the method of calculating the area of ​​a circle in JavaScript can be implemented through functions, objects, classes, etc. The simple mathematical problem of calculating the area of ​​a circle can be easily implemented in programming.

In practice, it can be applied flexibly according to the actual situation. Of course, for such a basic calculation method, it is recommended to use it appropriately in projects in actual production.

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