19-2.txt

Javascript语言开发经典教程开发

<!-- Check whether JavaScript 1.2 is supported. -->
<SCRIPT LANGUAGE="JavaScript1.2">var _js12_ = 1.2</SCRIPT>

<!-- Now avoid the problems with JavaScript 1.2 on Navigator by running -->
<!-- the following code on any browser that supports JavaScript 1.1. If -->
<!-- the browser does not support JavaScript 1.2, however, we'll display -->
<!-- an error message and suppress any syntax errors that occur. -->
<SCRIPT LANGUAGE="JavaScript1.1">
// If JavaScript 1.2 is not supported, fail gracefully.
if (!_js12_) {
    alert("This program requires a browser with JavaScript 1.2 support");
    window.onerror = new Function("return true;");
}

// Now proceed with the JavaScript 1.2 code. 
</SCRIPT>