Science Knowings: JavaScript Course For Social Media

Loops (for, while, do-while)

Looping: Loops (for, while, do-while)

Previously on Switch Statements

We covered the basics of switch statements, including their syntax and how to use them for decision-making.

Loops: Our New Adventure

Today, we'll explore looping constructs for, while, and do-while that allow us to execute code repeatedly.

Why Loops?

Loops are essential for automating repetitive tasks, such as iterating through arrays, performing calculations, and processing data.

They help us write concise and efficient code, reducing the need for manual repetitions.

Types of Loops

JavaScript offers three main types of loops:

  • for Loops: Use a counter variable to iterate over a specific range or array.
  • while Loops: Continue executing the loop as long as a condition remains true.
  • do...while Loops: Similar to while loops, but always execute the loop at least once, regardless of the initial condition.

for Loops: A Closer Look

for (initialization; condition; increment/decrement) {
    statement 1;
    statement 2;


  • Initialization: Variable initialized before the loop starts.
  • Condition: Evaluated before each iteration. Loop continues if true.
  • Increment/Decrement: Updates the variable after each iteration.

for...of Loops: Enhanced Iteration

ES6 introduced for...of loops, specifically designed for iterating over iterable objects, such as arrays.

for (variable of iterable) {

while Loops: Conditional Execution

while (condition) {

Key Points:

  • Checks the condition before executing the loop.
  • Continues looping as long as the condition remains true.

do...while Loops: Guaranteed Execution

do {
} while (condition);

Key Features:

  • Executes the loop at least once, regardless of the condition.
  • Checks the condition after the loop execution.

When to Use Each Loop Type

for Loops:
 Iterating over a known number of times or array elements.

while Loops:
 Iterating until a condition becomes false.

do...while Loops:
 When you want guaranteed execution at least once, usually with user input or data validation.

Loop Control Statements (break, continue)

 Terminates the loop immediately and transfers control to the code after the loop.

 Skips the current iteration of the loop and continues to the next one.

Nested Loops: Loops Within Loops

Multiple loops can be nested within each other to create complex iterations.

for (i = 0; i < 5; i++) {
    for (j = 0; j < 5; j++) {
        // Nested loop code

Real-World Examples of Loops

Loops are used extensively in practical applications, including:

  • Iterating through arrays to process elements.
  • Calculating sums, averages, and other statistical measures.
  • Creating interactive user interfaces with dynamic content.

Common Looping Mistakes

Infinite Loops:
 Failing to increment or update the loop variable properly, resulting in an endless loop.

Off-by-One Errors:
 Incorrect loop boundaries, leading to missing or extra iterations.

Best Practices for Looping

Clear Loop Conditions:
 Ensure loop conditions are well-defined and easy to understand.

Code Reuse:
 Extract common loop logic into reusable functions for better code organization.

Next Topic: Functions

Functions: Our Next Adventure

In the next session, we'll explore functions, which are essential for organizing code, reducing duplication, and creating reusable components.

Stay Tuned!