19-1.txt

Javascript语言开发经典教程开发

<!-- Set a variable to determine what version of JavaScript we support. -->
<!-- This technique can be extended to any number of language versions. -->
<SCRIPT LANGUAGE="JavaScript"> var _version = 1.0; </SCRIPT>
<SCRIPT LANGUAGE="JavaScript1.1">  _version = 1.1; </SCRIPT>
<SCRIPT LANGUAGE="JavaScript1.2">  _version = 1.2; </SCRIPT>

<!-- Run this code on any JavaScript-enabled browser.  -->
<!-- If the version is not high enough, display a message. -->
<SCRIPT LANGUAGE="JavaScript">
  if (_version < 1.1) {
    document.write('<HR><H1>This Page Requires JavaScript 1.1</H1>');
    document.write('Your JavaScript 1.0 browser cannot run this page.<HR>');
  }
</SCRIPT>

<!-- Now run the actual program only on JavaScript 1.1 browsers. -->
<SCRIPT LANGUAGE="JavaScript1.1">
    // The actual JavaScript 1.1 code goes here.
</SCRIPT>