As we’ll be using the browser as our demo environment, let’s see a couple of functions to interact with the user:
This one we’ve seen already. It shows a message and waits for the user to press “OK”.
The mini-window with the message is called a modal window. The word “modal” means that the visitor can’t interact with the rest of the page, press other buttons, etc, until they have dealt with the window. In this case – until they press “OK”.
prompt accepts two arguments:
result = prompt(title, [default]);
It shows a modal window with a text message, an input field for the visitor, and the buttons OK/Cancel.
- The text to show the visitor.
- An optional second parameter, the initial value for the input field.
The square brackets around
default in the syntax above denote that the parameter as optional, not required.
The visitor can type something in the prompt input field and press OK. Then we get that text in the
result. Or they can cancel the input by pressing Cancel or hitting the Esc key, then we get
null as the
The call to
prompt returns the text from the input field or
null if the input was canceled.
The second parameter is optional, but if we don’t supply it, Internet Explorer will insert the text
"undefined" into the prompt.
Run this code in Internet Explorer to see:
So, for prompts to look good in IE, we recommend always providing the second argument:
result = confirm(question);
confirm shows a modal window with a
question and two buttons: OK and Cancel.
The result is
true if OK is pressed and
We covered 3 browser-specific functions to interact with visitors:
- shows a message.
- shows a message asking the user to input text. It returns the text or, if Cancel button or Esc is clicked,
- shows a message and waits for the user to press “OK” or “Cancel”. It returns
truefor OK and
All these methods are modal: they pause script execution and don’t allow the visitor to interact with the rest of the page until the window has been dismissed.
There are two limitations shared by all the methods above:
- The exact location of the modal window is determined by the browser. Usually, it’s in the center.
- The exact look of the window also depends on the browser. We can’t modify it.
That is the price for simplicity. There are other ways to show nicer windows and richer interaction with the visitor, but if “bells and whistles” do not matter much, these methods work just fine.