thoughtworks-jumpstart / javascript-classes

JavaScript Classes

Let's put our knowledge of classes to practice! In this assignment, you will create JavaScript objects that model real life objects using classes as a blueprint.

Instructions:

• Use node to run the JavaScript files created in the exercises below.

1. Model a Rectangle

• create a file named Rectangle.js

• in it, create a class named Rectangle, with the following properties in the constructor:

  • breadth
  • length

• define a method named area() to return the area of the rectangle

  • formula: area = length * breadth

• instantiate the following rectangles one by one and verify that area() returns the expected values as stated below

  • you can use console.log to log the results and verify them

breadth	length	area()	perimeter()
2	4	8	12
5	10	50	30

Repeat these steps for perimeter()

• formula: perimeter = 2 * length + 2 * breadth

2. Model a Circle

• create a file named Circle.js
• in it, create a class named Circle, with the following property in the constructor:
  • radius
• define a method named area() to return the area of the circle
  • formula: area = Math.PI * r ** 2
  • hint: search "how to round a number to 1 decimal place" on google to find out how to generate the output as required
• instantiate the following circles one by one and verify that area() returns the expected values as stated below

radius	area()	perimeter()
1	3.1	6.3
2	12.6	12.6
3	28.3	18.8

Repeat these steps for perimeter()

• formula: perimeter = 2 * Math.PI * r

3. Bonus: Model a SimpleCalculator

• For this bonus exercise, don't use assertEquals. Instead, console.log to see the output of your methods and manually check whether it matches your expected values
• create a file named SimpleCalculator
• in it, create a class named SimpleCalculator, with the following property in the constructor:
  • value (this will be the starting value). If no argument is supplied during instantiation, value should default to 0
• Implement (i.e. write code for) the following methods.
  • calculator.add(n)
  • calculator.subtract(n)
  • calculator.multiply(n)
  • calculator.divide(n)
• Implementation logic for each method:
  • take in one argument (n)
  • use n to update the value of this.value
  • return this so that we can chain methods (example: calculator.add(12).multiply(2).divide(2))

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