INTRODUCTION TO JAVASCRIPT

JavaScript is a high-level, dynamic programming language commonly used to create interactive effects within web browsers.

Key Concepts:

• Variables and Data Types
• Operators
• Control Flow (Conditionals and Loops)
• Functions
• Objects and Arrays
• Event Handling

VARIABLES AND DATA TYPES

VARIABLES

Variables are containers for storing data values.

Syntax:

javascriptCopy codelet x = 5;
const y = "Hello";
var z = true;

Data Types:

1. Number: Represents numeric values.javascriptCopy codelet age = 25;let price = 19.99;
2. String: Represents text.javascriptCopy codelet name = "John";
3. Boolean: Represents logical values, true or false.javascriptCopy codelet isStudent = true;
4. Array: Represents a collection of items.javascriptCopy codelet colors = ["red", "green", "blue"];
5. Object: Represents a collection of properties.javascriptCopy codelet person = { firstName: "Jane", lastName: "Doe", age: 30};

OPERATORS

Operators are used to perform operations on variables and values.

Examples:

• Arithmetic Operators: +, -, *, /, %
• Assignment Operators: =, +=, -=, *=, /=
• Comparison Operators: ==, ===, !=, !==, <, >, <=, >=
• Logical Operators: &&, ||, !

CONTROL FLOW

CONDITIONAL STATEMENTS

Used to perform different actions based on different conditions.

Examples:

javascriptCopy codeif (age > 18) {
  console.log("Adult");
} else {
  console.log("Minor");
}

LOOPS

Used to execute a block of code a number of times.

Examples:

• for loop:javascriptCopy codefor (let i = 0; i < 5; i++) { console.log(i);}
• while loop:javascriptCopy codelet i = 0;while (i < 5) { console.log(i); i++;}

FUNCTIONS

Functions are blocks of code designed to perform a particular task.

Syntax:

javascriptCopy codefunction greet(name) {
  return "Hello " + name;
}
console.log(greet("Alice"));

OBJECTS AND ARRAYS

OBJECTS

Objects are collections of properties.

Example:

javascriptCopy codelet car = {
  make: "Toyota",
  model: "Corolla",
  year: 2020
};
console.log(car.make); // Outputs: Toyota

ARRAYS

Arrays are used to store multiple values in a single variable.

Example:

javascriptCopy codelet fruits = ["apple", "banana", "cherry"];
console.log(fruits[0]); // Outputs: apple

EVENT HANDLING

JavaScript can respond to user actions such as clicks and key presses.

Example:

javascriptCopy codedocument.getElementById("myButton").onclick = function() {
  alert("Button clicked!");
};

SAMPLE QUESTIONS AND EXPLANATIONS

1. Question: What are the main data types in JavaScript and how would you declare a variable for each type?Answer:
   • Number: let age = 25;
   • String: let name = "John";
   • Boolean: let isStudent = true;
   • Array: let colors = ["red", "green", "blue"];
   • Object: let person = { firstName: "Jane", lastName: "Doe", age: 30 };
2. Question: What is the difference between let, const, and var?Answer:
   • let allows you to declare variables that can be reassigned.
   • const is used to declare variables that cannot be reassigned.
   • var is the old way to declare variables and is function-scoped.
3. Question: Write a function in JavaScript that takes two numbers and returns their sum.Answer:javascriptCopy codefunction add(a, b) { return a + b;}console.log(add(5, 3)); // Outputs: 8