How to name variables in JavaScript?

Variables can be thought of as named containers. You can place data into these containers and then refer to the data simply by naming the container.

While naming your variables in JavaScript, keep the following rules in mind.

Variable Naming Rules

• You should not use any of the JavaScript reserved keywords as a variable name. These keywords are mentioned in the next section. For example, break or boolean variable names are not valid.
• JavaScript variable names should not start with a numeral (0-9). They must begin with a letter or an underscore character. For example, 123test is an invalid variable name but _123test is a valid one.
• JavaScript variable names are case-sensitive. For example, Name and name are two different variables.

Valid Variable Names

// Valid variable names
let userName = "John";
let _score = 100;
let $price = 29.99;
let age2 = 25;
let firstName = "Alice";

console.log(userName);
console.log(_score);
console.log($price);

John
100
29.99

Invalid Variable Names

// These will cause syntax errors
let 2age = 25;        // Cannot start with number
let for = "loop";     // Cannot use reserved keyword
let my-name = "Bob";  // Hyphens not allowed
let my name = "Bob";  // Spaces not allowed

Case Sensitivity Example

let name = "lowercase";
let Name = "Capitalized";
let NAME = "UPPERCASE";

console.log(name);    // Different variable
console.log(Name);    // Different variable  
console.log(NAME);    // Different variable

lowercase
Capitalized
UPPERCASE

Best Practices

• Use camelCase for multi-word variables: firstName, totalScore
• Choose descriptive names: userAge instead of a
• Use const for values that won't change: const PI = 3.14159
• Avoid abbreviations that aren't clear: userName instead of usrNm

Conclusion

Follow JavaScript's naming rules and use descriptive, camelCase names for better code readability. Avoid reserved keywords and numbers at the start of variable names.