**Course Title:** Modern JavaScript Programming: From Fundamentals to Full-Stack Development **Section Title:** Control Structures and Functions **Topic:** Conditionals (if, else, switch) and looping structures (for, while, forEach). **Overview** ------------ In this topic, we'll explore the fundamental control structures in JavaScript, which enable you to write more efficient, modular, and scalable code. We'll delve into conditionals (if, else, switch) and looping structures (for, while, forEach), and provide examples to demonstrate their usage. **Conditional Statements** ------------------------- Conditional statements are used to execute different blocks of code based on specific conditions. There are three main types of conditional statements in JavaScript: ### 1. If Statement The if statement executes a block of code if the specified condition is true. **Syntax:** ```javascript if (condition) { // code to be executed } ``` **Example:** ```javascript let age = 25; if (age >= 18) { console.log("You are an adult."); } ``` In this example, the code inside the if block will be executed because the condition `age >= 18` is true. ### 2. If-Else Statement The if-else statement executes a block of code if the specified condition is true, and another block of code if the condition is false. **Syntax:** ```javascript if (condition) { // code to be executed if true } else { // code to be executed if false } ``` **Example:** ```javascript let temperature = 25; if (temperature > 30) { console.log("It's hot outside."); } else { console.log("It's not hot outside."); } ``` In this example, the code inside the else block will be executed because the condition `temperature > 30` is false. ### 3. Switch Statement The switch statement executes a block of code based on the value of a variable or expression. **Syntax:** ```javascript switch (variable) { case value1: // code to be executed if variable matches value1 break; case value2: // code to be executed if variable matches value2 break; default: // code to be executed if variable doesn't match any value break; } ``` **Example:** ```javascript let day = "Monday"; switch (day) { case "Monday": console.log("It's Monday."); break; case "Tuesday": console.log("It's Tuesday."); break; default: console.log("It's not Monday or Tuesday."); break; } ``` In this example, the code inside the first case block will be executed because the value of `day` matches "Monday". **Looping Structures** --------------------- Looping structures are used to execute a block of code repeatedly for a specified number of iterations. ### 1. For Loop The for loop executes a block of code for a specified number of iterations. **Syntax:** ```javascript for (initialization; condition; increment) { // code to be executed } ``` **Example:** ```javascript for (let i = 0; i < 5; i++) { console.log(`Iteration ${i}`); } ``` In this example, the code inside the for loop will be executed 5 times. ### 2. While Loop The while loop executes a block of code while a specified condition is true. **Syntax:** ```javascript while (condition) { // code to be executed } ``` **Example:** ```javascript let i = 0; while (i < 5) { console.log(`Iteration ${i}`); i++; } ``` In this example, the code inside the while loop will be executed 5 times. ### 3. forEach Loop (Array Method) The forEach loop executes a block of code for each element in an array. **Syntax:** ```javascript array.forEach((element, index) => { // code to be executed }); ``` **Example:** ```javascript let colors = ["red", "green", "blue"]; colors.forEach((color, index) => { console.log(`Color ${index}: ${color}`); }); ``` In this example, the code inside the forEach loop will be executed for each element in the `colors` array. **Key Concepts** * Conditional statements (if, else, switch) are used to execute different blocks of code based on specific conditions. * Looping structures (for, while, forEach) are used to execute a block of code repeatedly for a specified number of iterations. * The for loop is used to execute a block of code for a specified number of iterations. * The while loop is used to execute a block of code while a specified condition is true. * The forEach loop is used to execute a block of code for each element in an array. **Practical Takeaways** * Use conditional statements to execute different blocks of code based on specific conditions. * Use looping structures to execute a block of code repeatedly for a specified number of iterations. * Use the for loop for simple iterations. * Use the while loop for more complex iterations. * Use the forEach loop for iterating over arrays. **Additional Resources** * [MDN Web Docs: Conditional Statements](https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/conditionals) * [MDN Web Docs: Looping Structures](https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/loops) **What's Next?** In the next topic, we'll explore defining and invoking functions in JavaScript. **Got Questions or Need Help?** Please feel free to leave a comment below if you have any questions or need help with any of the concepts covered in this topic.