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JavaScript Tutorial >> JavaScript Prompts.


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In this session of JavaScript Tutorial we'll look at the JavaScript prompt. The prompt() is a method of the window object in JavaScript, just like JavaScript alert() or JavaScript confirm().

Well, let's say we wanted to get somebody's name before they saw our page, and then write their name on our web page right before their very eyes.......Well, we can do this using a JavaScript prompt. Here's the command of JavaScript Prompt.

Syntax of JavaScript Prompt.

prompt(' Enter your question to ask.', ' ');

Above line of JavaScript Prompt will bring up a window asking the question of your choosing, with a space for the viewer to answer. The second set of quotes allows us to enter any default answer. If we leave it blank, the viewer will just see an empty box ready to be typed in. This is usually done before the webpage loads, so that we can write the answer they give into our page.

Example of JavaScript Prompts

Now, for the JavaScript that made this work. Note how the prompt and if/else statements are in the HEAD section, while the actual writing of the name occurs in the BODY section of webpage.


<HEAD>
<SCRIPT language="JavaScript">
<!--Comments start
var enteredname= prompt('Please enter your name, so you can get a special greetings from us...', ' ');

 if ( (enteredname==' ') || (enteredname==null) )
 {
   enteredname="dear visitor, you didn't specify your name...";
 }

//--> Comments ending
</SCRIPT>

</HEAD>

<BODY>

<SCRIPT language="JavaScript">
<!-- Comments start
  document.write("<CENTER><H1>Hello, " + enteredname+ " ! |
  Welcome at Global Guide Line Technology, JavaScript Tutorial...!
  <\/H1><\/CENTER>");

//--> 
</SCRIPT>

</BODY>

The first thing that happens is that the JavaScript Variable enteredname is assigned the value it receives from the user from the JavaScript Prompt. So the JavaScript Variable enteredname will be a string of characters that makes up the person's name. The if/else statement assigns enteredname a value of "Dude" if nothing is entered in the prompt by the user. It checks for " " and for null, and both are pretty much nothing. Now, in the BODY section, we again use the JavaScript SCRIPT tags to set off the JavaScript from any HTML around it. We will also see a new command called document.write(" "); . This is what allows the JavaScript variable enteredname to be written onto the HTML document. We are writing two strings plus our variable, enteredname. The JavaScript variable enteredname is not in quotes because it is a value and not itself a string but it's value is a string. That's why we have the plus signs around it....It makes the browser write the first string plus the JavaScript variable plus the second string. Now, notice the HTML tags are inside the strings! Since this is a JavaScript, the only way to write the HTML tags back to the page is by including them inside the quotes as part of the string. Also, we probably noticed the way the closing tags were written differently. (<\/H1>). The backslash is there as the JavaScript escape character. It allows us to write the forward slash without it being mistaken for a division sign! (Remember / is division in JavaScript Tutorial). Thus using the backslash followed by a forward slash ultimately gives us....... our single forward slash. Pretty nifty trick, isn't it?

Well, that does it for now. Let's go check out the above code and examine and analyses in reality, test your self JavaScript Prompts Example.


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JavaScript Alert, Confirmation and Prompt Boxes Examples



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