1. Variables:

   • var, let, const: Keywords to declare variables with different scoping rules.

     • Explanation: Variables are used to store and manipulate data in JavaScript. The var keyword has function scope, let has block scope, and const declares a constant variable.

     • Example: var x = 5; // x is accessible within the function it's declared in

       let y = 10; // y is accessible only within the block it's declared in

       const z = 15; // z is a constant variable that cannot be reassigned

2. Data Types:

   • String: Represents textual data.

     • Explanation: Strings are sequences of characters enclosed in single or double quotes.

     • Example: let name = "John";

   • Number: Represents numeric data.

     • Explanation: Numbers can be whole numbers or decimal numbers.

     • Example: let age = 25;

   • Boolean: Represents either true or false.

     • Explanation: Booleans are used to represent logical values.

     • Example: let isStudent = true;

   • Array: Represents an ordered collection of values.

     • Explanation: Arrays allow you to store multiple values in a single variable.

     • Example: let numbers = [1, 2, 3, 4, 5];

   • Object: Represents a collection of key-value pairs.

     • Explanation: Objects allow you to store related data as properties and their values.

     • Example: let person = { name: "John", age: 25 };

3. Operators:

   • Arithmetic Operators: Perform arithmetic operations.

     • Explanation: Arithmetic operators are used for basic math calculations.

     • Example: let sum = 5 + 3; (sum will be 8)

   • Assignment Operators: Assign values to variables.

     • Explanation: Assignment operators are used to assign values to variables.

     • Example: let x = 10; (x will be 10)

   • Comparison Operators: Compare values.

     • Explanation: Comparison operators compare values and return a boolean result.

     • Example: let isGreater = 5 > 3; (isGreater will be true)

   • Logical Operators: Perform logical operations.

     • Explanation: Logical operators are used to combine or negate boolean values.

     • Example: let isTrue = true && false; (isTrue will be false)

   • String Concatenation: Concatenates strings.

     • Explanation: The + operator is used to concatenate strings.

     • Example: let fullName = "John" + " Doe"; (fullName will be "John Doe")

4. Control Flow:

   • Conditional Statements:

     • if statement: Executes a block of code if a condition is true.

       • Explanation: The if statement allows you to perform different actions based on different conditions.

       • Example: if (age >= 18) { console.log("You are an adult."); } else { console.log("You are a minor."); }

     • switch statement: Executes different blocks of code based on different cases.

       • Explanation: The switch statement allows you to choose one of many code blocks to be executed.

       • Example: switch (day) { case "Monday": console.log("Today is Monday."); break;

5. Loops:

   • for loop: Executes a block of code repeatedly for a specified number of times.

     • Explanation: The for loop allows you to iterate over a block of code a specific number of times.

     • Example: for (let i = 0; i < 5; i++) { console.log(i); }

   • while loop: Executes a block of code repeatedly as long as a condition is true.

     • Explanation: The while loop repeatedly executes a block of code as long as a given condition is true.

     • Example: while (count < 10) { console.log(count); count++; }

6. Functions:

   • Declaration: Define reusable blocks of code.

     • Explanation: Functions allow you to define reusable blocks of code that can be called multiple times.

     • Example: function greet(name) { console.log("Hello, " + name + "!"); }

   • Arrow Functions: A concise syntax for defining functions.

     • Explanation: Arrow functions provide a shorter syntax for writing functions, especially useful for one-liners.

     • Example: const sum = (a, b) => a + b;

7. Arrays:

   • Array Methods:

     • push(): Add elements to the end of an array.

     • pop(): Remove the last element of an array.

     • length: Get the length of an array.

     • Explanation: Arrays have built-in methods that allow you to manipulate and retrieve data.

     • Example: let numbers = [1, 2, 3]; numbers.push(4); // Adds 4 to the end of the array console.log(numbers.length); // Outputs 4

8. Objects:

   • Object Properties: Accessing and modifying object properties.

     • Explanation: Objects have properties that can be accessed and modified using dot notation or bracket notation.

     • Example: let person = { name: "John", age: 25 }; console.log(person.name); // Outputs "John" person.age = 30; // Modifies the age property

9. String Methods:

   • length: Get the length of a string.

   • toUpperCase(): Convert a string to uppercase.

   • toLowerCase(): Convert a string to lowercase.

   • Explanation: Strings have built-in methods that allow you to perform operations and manipulations.

   • Example: let greeting = "Hello, World!"; console.log(greeting.length); // Outputs 13 console.log(greeting.toUpperCase()); // Outputs "HELLO, WORLD!"

10. Error Handling:

    • try, catch, finally: Handle and manage errors in JavaScript.

    • Explanation: Error handling allows you to catch and handle exceptions that occur during the execution of your code.

    • Example: try { // Code that may throw an error } catch (error) { // Code to handle the error } finally { // Code that runs regardless of whether an error occurred }

Learn more Javascript skills on Coursera.

JavaScript Courses | Web Development Courses | Node.Js Courses | MongoDB Courses | CSS Courses | React JS Courses | HTML Courses | Front End Web Development Courses