Parameters
The words inside the parentheses of functions are called parameters. The document.write() function requires one parameter: a string to write to your web page. The prompt() function takes two parameters: a string to write above the box and a string to write inside the box.
Parameters are the only aspect of a function you can control; they are your means of providing the function with the information it needs to do its job. With a prompt() function, for example, you can't change the color of the box, how many buttons it has, or anything else; in using a predefined prompt box, you've decided that you don't need to customize the box's appearance. You can only change the parameters it specifically provides—namely, the text and heading of ...
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