When you start writing advanced JavaScript code that contains a lot of complex information, you need a way to simplify and manipulate the information. JavaScript uses variables to simplify the statements and work with information. The variables act as containers to hold values.

You list the variables before the statements, like this:

var area = 4000;
var size = 200;

In this case, area is a variable, and its value is assigned to be 4000. size is also a variable, with a value of 200.

You can also list multiple variables by separating the variables with commas on the same line, like this:

var area = 4000, size = 200, distance = 100;

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Variables must be one word and can contain both letters and numbers (but can't start with numbers).

If the variable stores text (such as a phrase), the text is called a string. Strings are enclosed in quotes.

var welcome = "Welcome to the application.";

Single quotes are also acceptable instead of double quotes, but you must be consistent. You can't start with a double quote and end with a single quote.