hart.katie69
hart.katie69 May 8, 2026 • 0 views

JavaScript calculator code example for beginners

Hey there! 👋 Let's dive into creating a basic JavaScript calculator! It's a super fun project for beginners and really helps solidify your understanding of JavaScript fundamentals. I've put together a quick study guide and a practice quiz to help you master the concepts. Good luck and have fun coding! 💻
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laura.burton Jan 2, 2026

📚 Quick Study Guide

  • Basic Arithmetic Operators: JavaScript uses `+` (addition), `-` (subtraction), `*` (multiplication), `/` (division), and `%` (modulus).
  • 🧮 Variables: Use `let`, `const`, or `var` to store numbers and results. For example, `let num1 = 10;`
  • ✍️ Functions: Define functions to perform operations. For example, `function add(a, b) { return a + b; }`
  • 🕹️ Event Listeners: Attach event listeners to buttons to trigger calculations when clicked. Use `document.getElementById('myButton').addEventListener('click', myFunction);`
  • 🖥️ DOM Manipulation: Update the calculator display using `document.getElementById('result').value = myResult;`
  • ⚠️ Error Handling: Implement checks to handle division by zero or invalid inputs. Use `isNaN()` to check for non-numeric inputs.
  • 💡 Tips: Always convert input values to numbers using `parseFloat()` or `parseInt()` before performing calculations.

Practice Quiz

  1. Question 1: Which operator is used for addition in JavaScript?
    1. A) `+`
    2. B) `-`
    3. C) `*`
    4. D) `/`
  2. Question 2: How do you declare a variable in JavaScript?
    1. A) `variable x;`
    2. B) `let x;`
    3. C) `int x;`
    4. D) `string x;`
  3. Question 3: Which function is used to display output in an HTML element?
    1. A) `console.log()`
    2. B) `alert()`
    3. C) `document.getElementById().innerHTML`
    4. D) `prompt()`
  4. Question 4: What does DOM stand for?
    1. A) Document Object Model
    2. B) Data Object Model
    3. C) Digital Object Management
    4. D) Dynamic Object Management
  5. Question 5: Which function is used to convert a string to a number?
    1. A) `stringToNumber()`
    2. B) `parseInt()`
    3. C) `toNumber()`
    4. D) `convertToInt()`
  6. Question 6: How do you attach an event listener to a button in JavaScript?
    1. A) `button.listen('click', myFunction);`
    2. B) `button.onClick = myFunction;`
    3. C) `document.getElementById('myButton').addEventListener('click', myFunction);`
    4. D) `button.addEvent('click', myFunction);`
  7. Question 7: Which operator is used to find the remainder of a division?
    1. A) `/`
    2. B) `*`
    3. C) `%`
    4. D) `//`
Click to see Answers
  1. Answer: A) `+`
  2. Answer: B) `let x;`
  3. Answer: C) `document.getElementById().innerHTML`
  4. Answer: A) Document Object Model
  5. Answer: B) `parseInt()`
  6. Answer: C) `document.getElementById('myButton').addEventListener('click', myFunction);`
  7. Answer: C) `%`

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