JavaScript calculator code example for beginners

📚 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) `//`