react-state-calculator

React State Simple Calculator

In this exercise you build a simplified calculator application using React.

Learning Objectives

• Build a component that uses a useState hook to keep component state.
• Build a component with an onClick attribute that has a value of the function to invoke when the event is triggered
• Model the data a react application needs and create state hooks accordingly.

Set up

• Fork and clone this repository
• npm install to install dependencies
• npm start to start the React development server

Requirements

You are a required to implement a simplified calculator app.

• When the user presses a numbered button on either of the panels, the display above should be updated to show that number.
• When user presses the clear button, the display should be set back to 0
• When the user presses one of the operation buttons (+, -,*,÷) the operation display should be updated to show that operation.
• When the user presses the equals button the answer display should be updated to show the result of the calculation.

Tips

• Start by modelling the state of the application
• What state will you need to keep track of?
• What user interactions will modify that state and how?
• Start with one or two functional buttons and only consider the add operation. When you have that working, make additional buttons functional.

Extension 1

• Update your solution so the number panels act like a real calculator when inputting numbers
  • Numbers should appended, so pressing 1 then 2 should result in 12 being displayed
  • If the user presses a number while ‘0’ is displayed, the number should replace ‘0’ on the display. Subsequent numbers, including 0, are appended on to the display as usual.
  • If the user presses ‘0’ while ‘0’ is displayed, the display should remain at ‘0’. It should not be possible to define a number with leading zeros.

Extension 2

• Add a “store” button underneath the answer.
• When this button is clicked, the current answer should be stored in a state variable.
• Add a “recall” button to each of the number displays. When this button is clicked, the currently stored value should be shown on the corresponding number panel.

Extension 3

• Add a “.” button to the numbers panel of each section
• When the user presses this button, a decimal separator should be added to the number
• Only a single separator can be added to each number
• If no digit appears after the separator, the calculator should consider the number as having no separator (i.e. “1.” should be treated as “1”).
• Unlike whole numbers, leading zeros should be allowed after the separator. For example, “00001” is not valid, but “0.00001” is and “1.00001” is.