Let us first see the skeleton of a JavaScript file.

JavaScript code should be written between the tags. The value LANGUAGE = "JavaScript" indicates to the browser that Javascript code has been used in the HTML document. This is a good programming practice to comprise the Javascript code within the & tags.

Now let us start with variables. Variables store & retrieve data, also called as "values". A variable can refer to a value that changes or is changed. Variables are referred to through name, although the name you give them must conform to certain rules. A JavaScript identifier, or name, has to start with a letter or underscore ("_"); subsequent characters can also be digits (0-9). Since JavaScript is case sensitive, letters comprise the characters "A" through "Z" (uppercase) & the characters "a" by "z" (lowercase). Typically, variable names are selected to be meaningful and associated to the value they hold. For instance, a good variable name for containing the whole price of goods orders would be total price