Page 168 - DCAP408_WEB_PROGRAMMING

Web Programming

Notes Generally, the alert() method is used for exactly that – to warn the user or alert him or her to
something. Examples of this type of use include:

 Incorrect information in a form
 An invalid result from a calculation
 A warning that a service is not available on a given date
Nonetheless, the alert() method can still be used for friendlier messages.

Notes Note that Netscape alert boxes include the phrase “<url> [JavaScript Application]”
in the title bar of the alert while IE has “Microsoft Internet Explorerin the title bar of the
alert. Both have yellow triangles to “alert” you. This done in order to distinguish them
form those generated by the operating system or the browser. This done for security
reasons so that malicious programs cannot trick users into doing things they don’t want to
do.
<INPUT TYPE=”button” VALUE=”alert” onClick=”alert(‘This is an alert!!’)”>
OR
<INPUT TYPE=”button” VALUE=”alert” onClick=”window.alert(‘This is an
alert!!’)”>
The alert dialog box is used to display an alert message to the user.

prompt()

The alert() method still doesn’t enable you to interact with the user. The addition of the OK
button provides you with some control over the timing of events, but it still cannot be used to
generate any dynamic output or customize output based on user input.
The simplest way to interact with the user is with the prompt() method. The user needs to fill in
the field and then click OK.
prompt(“Enter Your Name:”, “Name”);

Notes

 You are providing two “arguments” to the method in the parenthesis. The prompt()
method “requires two pieces of information”. The first is text to be displayed, and
the second is the default data in the entry field.
 In JavaScript, when a method requires more than one argument, they are separated
by commas.

<INPUT TYPE=”button” VALUE=”prompt” onClick=”respPrompt()”>
The prompt() method dialog box allows the user the opportunity to enter information. It takes
two parameters; a message and a default string for the text entry field.
With function code:

<SCRIPT LANGUAGE=”JavaScript”>
function respPrompt() {

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