Variables are containers for storing values. All JavaScript variables must be identified with unique names. These unique names are called identifiers. Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume). The general rules for constructing names for variables (unique identifiers) are:

Nov 7, 2023 · Declaring variables is something you'll do all the time in JavaScript. And if you know the variable declaration process inside and out, you'll have the confidence to start writing great JS code. Through this article, you will learn how to declare and mutate variables using var , let , and const , and you'll get a better understanding of the ...

Mar 13, 2025 · var declarations, wherever they occur in a script, are processed before any code within the script is executed. Declaring a variable anywhere in the code is equivalent to declaring it at the top. This also means that a variable can appear to be used before it's declared.

Feb 10, 2025 · The var keyword is used to declare variables in JavaScript. It has been part of the language since its inception. When a variable is declared using var, it is function-scoped or globally-scoped, depending on where it is declared.

In JavaScript, a variable can be declared using var, let, const keywords. var keyword is used to declare variables since JavaScript was created. It is confusing and error-prone when using variables declared using var. let keyword removes the confusion and error of var. It is the new and recommended way of declaring variables in JavaScript.

Aug 24, 2024 · Understanding how to properly declare variables with var, let and const is crucial for any JavaScript developer. Mastering variable declaration allows you to: Yet developers often gloss over the intricate differences between JavaScript‘s three variable declarations.

Summary: in this tutorial, you’ll learn about JavaScript variables and how to use variables to store values in the application. A variable is a label that references a value like a number or string. Before using a variable, you need to declare it. To declare a variable, you use the var keyword followed by the variable name as follows:

var x = 1 declares variable x in current scope (aka execution context). If the declaration appears in a function - a local variable is declared; if it's in global scope - a global variable is declared. x = 1, on the other hand, is merely a property assignment.

var is the keyword that tells JavaScript you’re declaring a variable. x is the name of that variable. = is the operator that tells JavaScript a value is coming up next. 100 is the value for the variable to store. After you declare a variable, you can reference it by name elsewhere in your code.

Explore the different ways to define variables in JavaScript including var, let, and const. Learn the best practices for variable declaration.