JavaScript Loops
Loops are fundamental programming structures that allow you to execute a block of code multiple times. They are extremely useful when you want to automate repetitive tasks or iterate over collections like arrays or objects.
📌 Why Use Loops?
- Reduce repetitive code and improve maintainability
- Iterate over data structures like arrays, objects, and maps
- Perform repeated calculations efficiently
- Enable automation in web applications, such as generating lists dynamically
🔹 For Loop
The for loop is the most common type of loop. It repeats a block of code as long as a condition evaluates to true. The for loop has three parts:
- Initialization: Sets up the counter variable.
- Condition: Checked before every iteration; loop stops if false.
- Increment/Decrement: Updates the counter after each iteration.
🔸 While & Do...While Loop
while loops check the condition before execution, whereas do...while executes at least once.
📐 For...of Loop
The for...of loop iterates over iterable objects like arrays, strings, maps, and sets. It is simple and clean.
📌 For...in Loop
The for...in loop iterates over the keys (property names) of an object.
⚡ Special Keywords: break & continue
JavaScript provides break and continue to control loop execution.
- break: Exits the loop immediately.
- continue: Skips the current iteration and continues with the next.
🔹 Nested Loops
Loops can be nested inside another loop. Useful for multi-dimensional data like tables.
⚡ Break & Continue
break exits the loop early. continue skips the current iteration.
🎮 Practice: Student Grades System
Create a small system that iterates over students, filters high scorers, and counts passes.
💡 Challenges:
- Add average score calculation
- Highlight students who failed
- Sort students by score using loops
📚 Summary
- Loops allow repeated execution of code blocks.
for,while,do...while,for...of,for...inare commonly used loops.- Use
breakto exit a loop,continueto skip an iteration. - Nested loops are useful but can affect performance.
