JavaScript(JS) Variables

In JavaScript, variables are used to store data that can be used throughout a program. A variable is a named container that holds a value. You can think of a variable as a box that has a label on it and that contains a value.

To declare a variable in JavaScript, you use the var, let, or const keyword, followed by the name of the variable, and optionally, an initial value. Here's an example:

var message = "Hello, world!";
let count = 42;
const PI = 3.14159;

In this example, we've declared three variables:

• message is a variable of type string that has an initial value of "Hello, world!"
• count is a variable of type number that has an initial value of 42.
• PI is a constant that has a value of 3.14159. Constants cannot be changed once they are initialized.

You can also declare a variable without initializing it:

let name;

In this example, we've declared a variable called name without giving it an initial value. If you try to use this variable before giving it a value, you'll get an undefined error.

You can assign a new value to a variable at any time by using the assignment operator (=):

count = 10;

In this example, we've assigned a new value of 10 to the count variable.

JavaScript is a dynamically typed language, which means that you don't have to specify the data type of a variable when you declare it. The data type of a variable is determined dynamically based on the type of the value that is assigned to it.