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How to Code A Single Operation Calculator in JavaScript!

How to Code A Single Operation Calculator in JavaScript!

  • English
  • Programming
  • JavaScriptJavaScript
  • (1996)
  • Project length: 1h 28m

Let's JavaScript. Code along! The calculator allow you to add, subtract multiply and divide 2 numbers with or without a decimal point. Our calculator will also have A backspace and clear feature. Our calculator will automatically start new calculations after the equal to operator is clicked. Eval has not used!


Please download twitter bootstrap theme from


  1. A single operator calculator.
  2. Add, Subtract Multiply or Divide 2 numbers.
  3. Update the screen with custom messages in-case of invalid calculations such as 0 divided by 0.
  4. Clear the calculator screen (upon clicking the clear button, and each time a number button is clicked after a calculation).
  5. Add decimals.
  6. Code in a backspace key to delete the last character on the calculator screen . Please download twitter bootstrap theme from

User Story:

  1. User can add, subtract, multiply or divide 2 numbers.
  2. User cannot start a calculation with an operator sign.
  3. If calculation is invalid, then update the display to show an error message.
  4. The user can use the “DEL” button to delete the last number or operator.
  5. The user can clear the display and reset the calculator for a new calculation with the “C” button.
  6. The calculator resets when a user clicks on a number, after a calculation has been performed and the result is in the display.

Project Outline


  1. Introduction

  2. HTML & CSS

  3. Global Variables: Part 1

  4. Global Variables: Part 2

  5. function setValue(number): Part 1

6.function setValue(number): Part 2

  1. function oppClick(numericCode): Part 1

  2. function oppClick(numericCode): Part 2

  3. function equalClick( ): Part 1

  4. function equalClick( ): Part 2

  5. function clearButton( )

  6. function backspace( ): Part 1

  7. function backspace( ): Part 2

  8. function setDecimal( ): Part 1

  9. function setDecimal( ): Part 2

  10. function setOppString( )


Average rating

5(1996 Reviews)