**Course Title:** Mastering TypeScript: From Basics to Advanced Applications **Section Title:** Control Structures and Functions **Topic:** Conditional statements: if, else, switch ### Introduction In programming, conditional statements are used to control the flow of a program's execution based on certain conditions or decisions. In TypeScript, we use if, else, and switch statements to implement conditional logic. In this topic, we will explore the syntax, usage, and best practices for using conditional statements in TypeScript. ### If Statement The if statement is the most basic conditional statement in programming. It executes a block of code if a given condition is true. ```typescript if (condition) { // code to be executed if condition is true } ``` Example: ```typescript let age: number = 25; if (age >= 18) { console.log("You are eligible to vote."); } ``` ### If-Else Statement The if-else statement is used to execute one block of code if a condition is true and another block of code if the condition is false. ```typescript if (condition) { // code to be executed if condition is true } else { // code to be executed if condition is false } ``` Example: ```typescript let age: number = 15; if (age >= 18) { console.log("You are eligible to vote."); } else { console.log("You are not eligible to vote."); } ``` ### If-Else-If Statement The if-else-if statement is used to check multiple conditions and execute different blocks of code accordingly. ```typescript if (condition1) { // code to be executed if condition1 is true } else if (condition2) { // code to be executed if condition2 is true } else { // code to be executed if all conditions are false } ``` Example: ```typescript let age: number = 25; if (age >= 60) { console.log("You are a senior citizen."); } else if (age >= 18) { console.log("You are an adult."); } else { console.log("You are a minor."); } ``` ### Switch Statement The switch statement is used to execute different blocks of code based on the value of a variable. ```typescript switch (expression) { case value1: // code to be executed if expression === value1 break; case value2: // code to be executed if expression === value2 break; default: // code to be executed if expression does not match any case } ``` Example: ```typescript let day: string = "Monday"; switch (day) { case "Monday": console.log("Today is Monday."); break; case "Tuesday": console.log("Today is Tuesday."); break; default: console.log("Today is not Monday or Tuesday."); } ``` ### Best Practices * Always use curly brackets `{}` to define the block of code to be executed for a condition. * Use the `===` operator to check for equality, not the `==` operator. * Use the `switch` statement when you have multiple conditions to check, and the conditions are mutually exclusive. * Avoid using nested if-else statements, as they can make the code harder to read and maintain. ### Practical Takeaways * Use conditional statements to control the flow of a program based on conditions or decisions. * Use the `if` statement to execute a block of code if a condition is true. * Use the `if-else` statement to execute one block of code if a condition is true and another block of code if the condition is false. * Use the `switch` statement to execute different blocks of code based on the value of a variable. ### Resources * [TypeScript Documentation](https://www.typescriptlang.org/docs/handbook/basic-types.html#boolean) - Conditional Statements * [W3Schools](https://www.w3schools.com/typescript/typescript_boolean.asp) - Conditional Statements in TypeScript ### What's Next? In the next topic, we will cover loops in TypeScript, including the `for`, `while`, and `forEach` statements. Do you have any questions about conditional statements in TypeScript? Leave a comment or ask for help below.