Jiving with Javascript, Part IV
By Kevin M. Savetz
Now or Later?
Should you bother learning JavaScript now, or is it currently just a toy for experimenters? Should you wait until the final version of the JavaScript interpreter ships before trying to learn the ins and outs of the language? Augustine thinks that now is the time to get a jump start on JavaScripting. "Learn JavaScript right now if you want to capture the market while it is viable--you'll be ahead of the field. If you wait until it is fully functional before you learn it, I think you'll be behind the game," he says. Online tutorials can get you started with the basics of the language, and Internet mailing lists and newsgroups devoted to the topic are already home to thriving communities of developers and experimenters.
Will the serious Web page developer need to understand both Java and JavaScript? Because JavaScript can interact directly with the user anywhere on a Web page (rather than being limited to a single window, as with Java), most Java developers will probably want to learn both. But JavaScript should also be viable as a stand-alone tool for less experienced programmers who want to add interactivity to their Web pages.
Figure 1
A Simple JavaScript Program
<HEAD>
<SCRIPT LANGUAGE="JavaScript">
<!--- these comments should hide the script from old browsers
function checkNum(str, min, max) {
if (str == "") {
alert("Enter a number in the field, please.")
return false
}
for (var i = 0; i < str.length; i++) {
var ch = str.substring(i, i + 1)
if (ch < "0" || ch > "9") {
alert("Enter a number, please.")
return false
}
}
var val = parseInt(str, 10)
if ((val < min) || (val > max)) {
alert("Try a number from 1 to 10.")
return false
}
return true
}
function thanks() {
alert("Thank you.")
}
// end hiding from old browsers -->
</SCRIPT>
</HEAD>
<BODY>
<FORM NAME="ex5">
Please enter a number from 1 to 10:
<INPUT NAME="num"
onChange="if (!checkNum(this.value, 1, 10))
{this.focus();this.select();} else {thanks()}">
</FORM>
</BODY>
Kevin Savetz is author of MBONE: Multicasting Tomorrow's Internet, published by IDG books and waiting patiently on a bookshelf near you. You can visit Kevin's Web page or reach him at savetz@northcoast.com.
Reprinted from Web Developer® magazine, Vol. 2 No. 2 Spring 1996 (c) 1996 internet.com Corporation. All rights reserved.
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