The Rules of Naming

When you create a variable in JavaScript, you get to choose its name! However, JavaScript has strict rules about what you can and cannot name a variable.

1. Allowed Characters

Variable names can only contain:

• Letters (a-z, A-Z)
• Numbers (0-9)
• Underscores (_)
• Dollar signs ($)

2. Must Not Start With a Number

A variable name can contain a number, but it cannot start with one.

let player1 = "Himanshu"; // Valid
// let 1player = "Himanshu"; // Invalid - throws an error!

3. Case Sensitivity

JavaScript is strictly case-sensitive. This means myAge, myage, and MYAGE are treated as three completely different variables.

4. No Reserved Keywords

You cannot use JavaScript's built-in keywords as variable names. For example, you cannot name a variable let, if, function, or return.

Best Practices (Conventions)

While the rules above are mandatory, developers also follow conventions (best practices) to make code readable:

• Camel Case: The most common naming convention in JavaScript. The first word is lowercase, and every subsequent word starts with an uppercase letter.
  • Example: firstName, totalPriceOfItems.
• Descriptive Names: Always use names that describe the data. Use let userAge = 25; instead of let x = 25;. It makes your code self-documenting!

💡 Himanshu's Tip:

Get into the habit of using camelCase immediately! It is the undisputed industry standard for JavaScript. If you go to a technical interview and write let user_age, the interviewer will immediately know you might be primarily a Python developer.

Interview Questions

1. Can a JavaScript variable name start with a number?
2. Are myVariable and myvariable considered the same in JavaScript? Why or why not?
3. What is camelCase formatting?