Introduction to JavaScript Fundamentals II

In JavaScript, a loop is a control structure that repeats a set of instructions and a function is a reusable block of logic that you can call whenever you need it.

Together, they let you go beyond "scripts that run top to bottom" and start writing programs that can process input, handle multiple cases, and scale without duplicating code.

Loops and functions are commonly used to:

• Iterate over data (characters, arrays, object entries) and build output step by step.
• Apply the same rules to many items (validation, formatting, transformations).
• Encapsulate logic into small named operations (easy to reuse and easier to test).
• Build features by composition (a big problem becomes a chain of smaller functions).

Learning objectives

In this module, you'll learn how to repeat and reuse logic in JavaScript using two essential building blocks: loops and functions.

These two concepts are at the core of writing real programs in Node.js: parsing user input, iterating over data, generating output, validating payloads, and composing your logic into small reusable components.

After completing this module, you will be able to:

• Repeat instructions automatically using the while and for loops.
• Decide when a loop should stop based on a condition or a counter.
• Encapsulate a set of statements into reusable functions.
• Define and invoke functions that accept parameters and return values.
• Use anonymous functions and arrow functions to define inline behavior.
• Break down a bigger problem into smaller functions that can be tested independently.
• Build complete scripts that generate output based on user-defined inputs.