How do you define a variable in JavaScript?

In JavaScript, a variable is used to store data values. To define a variable, you use the keyword var followed by the name of the variable. Here is the basic syntax:

var variableName;

Example:

To create a variable named "myVariable" that stores the value 10, you would write:

var myVariable = 10;

In this example, the variable myVariable is declared and initialized with the value 10. You can also declare a variable without initializing it, like this:

var anotherVariable;

Variables in JavaScript can store various types of data such as numbers, strings, arrays, objects, functions, and more. You can also change the value of a variable by simply assigning a new value to it, like this:

myVariable = 20;

It's important to note that JavaScript is a dynamically typed language, so you don't need to specify the data type of a variable when defining it. The interpreter determines the data type based on the value assigned to the variable.