Understanding JavaScript Statements and Comments

This tutorial introduces the fundamental building blocks of JavaScript: statements and comments. Understanding these concepts is crucial for writing clear, efficient, and maintainable JavaScript code.

Table of Contents

• JavaScript Statements
• JavaScript Comments

JavaScript Statements

A JavaScript statement is a single instruction that the JavaScript engine executes. These instructions form the core logic of your programs. Statements can be simple or complex, but they fundamentally represent a single action. While not strictly required in all cases, it’s best practice to always terminate statements with a semicolon (;) to ensure predictable behavior and avoid potential errors.

Examples of JavaScript Statements:

• Variable Declaration and Assignment: let x = 10; declares a variable x and assigns it the value 10. const PI = 3.14159; declares a constant variable.
• Assignment: y = 20; assigns the value 20 to the variable y (Note: While permissible in some contexts, always declare variables using let or const for better code clarity and maintainability).
• Function Call: console.log("Hello, world!"); calls the built-in console.log() function to display output.
• Arithmetic Operation: z = x + y; adds x and y, assigning the result to z.
• Conditional Statement: if (x > y) { console.log("x is greater than y"); } executes code based on a condition.
• Loop: for (let i = 0; i < 10; i++) { console.log(i); } executes a block of code repeatedly.

Statements are executed sequentially, from top to bottom, unless control flow statements (like if, for, while) alter the execution order.

JavaScript Comments

Comments are essential for code readability and maintainability. They are explanatory notes within your code that the JavaScript engine ignores. Effective commenting makes your code easier to understand, debug, and collaborate on, particularly in larger projects.

Types of JavaScript Comments:

• Single-line Comments: Use // to create a single-line comment. // This is a single-line comment.
• Multi-line Comments: Use /* and */ to create multi-line comments.

  /*
  This is a multi-line comment.
  It can span multiple lines.
  */
  

Remember to write clear, concise comments that explain the why behind your code, not just the what. Focus on explaining complex logic or non-obvious parts of your code.