Understanding JavaScript Syntax

Every programming language follows a set of rules called syntax.

Syntax defines how code should be written and structured.

If syntax rules are not followed, JavaScript will generate errors and fail to execute properly.

Therefore, understanding syntax is essential before learning advanced topics.

Statements

A statement is an instruction that tells the browser to perform an action.

Example:

console.log("Hello");
alert("Welcome");

Each line above is a separate statement.

JavaScript executes statements in the order they appear.

Keywords

Keywords are reserved words with special meanings.

Common JavaScript keywords include:

• Let
• Const
• If
• Else
• For
• While
• Function
• return

These words cannot be used as variable names.

Example:

let username = "Ritik";

Here, let is a keyword used to declare a variable.

Identifiers

Identifiers are names assigned to variables, functions, and other programming elements.

Example:

let studentName = "Ritik";

In this example, studentName is an identifier.

Rules for Identifiers

• Must start with a letter, underscore (_) or dollar sign ($)
• Cannot start with a number
• Cannot contain spaces
• Cannot use JavaScript keywords
• Can contain letters and numbers

Valid Examples:

• username
• _age
• $price
• student1

Invalid Examples:

• 1name
• user name
• let

Comments

Comments are notes written inside code.

The browser ignores comments during execution.

Single-Line Comment

// This is a comment

Multi-Line Comment

/*
This is a
multi-line comment
*/

Comments improve readability and make code easier to maintain.

Case Sensitivity

JavaScript is case-sensitive.

This means uppercase and lowercase letters are treated differently.

Example:

let name = "Ritik";
let Name = "Kumar";

Here, name and Name are different variables.

Because of this, developers must pay close attention to capitalization.