Control Structures: Loops JavaScript

What You’ll Learn 📚

• Understanding what loops are and why we use them.
• Key terminology related to loops.
• Different types of loops in JavaScript.
• Practical examples to illustrate each type of loop.
• Common questions and troubleshooting tips.

Introduction to Loops

Loops are a fundamental concept in programming that allow us to repeat a block of code multiple times. Imagine you want to print numbers from 1 to 10. You could write ten separate console.log statements, but that’s not efficient. Instead, we use loops to automate repetitive tasks!

Key Terminology

• Iteration: Each time a loop runs, it’s called an iteration.
• Loop Body: The block of code that is executed with each iteration.
• Condition: A statement that determines whether the loop should continue running.

Types of Loops in JavaScript

The for Loop

// Simple example of a for loop
for (let i = 1; i <= 10; i++) {
    console.log(i); // This will print numbers from 1 to 10
}

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The while Loop

// Simple example of a while loop
let i = 1;
while (i <= 10) {
    console.log(i); // This will print numbers from 1 to 10
    i++;
}

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The do...while Loop

// Simple example of a do...while loop
let i = 1;
do {
    console.log(i); // This will print numbers from 1 to 10
    i++;
} while (i <= 10);

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Common Questions and Answers

1. What is the difference between for and while loops?

   The for loop is typically used when the number of iterations is known. The while loop is used when the number of iterations is not known and depends on a condition.

2. Can a loop run indefinitely?

   Yes, if the condition never becomes false, the loop will run indefinitely, causing an infinite loop. Be careful with loop conditions!

3. How can I stop a loop early?

   You can use the break statement to exit a loop prematurely.

4. What is a common mistake with loops?

   A common mistake is forgetting to update the loop variable, which can lead to infinite loops.

Troubleshooting Common Issues

Infinite Loops: Ensure your loop condition will eventually become false. Double-check your loop variable updates.

Lightbulb Moment: Use console.log statements inside your loop to debug and understand how your loop is executing.

Practice Exercises

• Write a for loop that prints even numbers from 2 to 20.
• Create a while loop that prints numbers from 10 to 1 in descending order.
• Use a do...while loop to print the first 5 multiples of 3.

Try these exercises on your own, and remember, practice makes perfect! 💪

Additional Resources

• MDN Web Docs: Loops and iteration
• W3Schools: JavaScript For Loop