Differences

This shows you the differences between two versions of the page.

--- docs:programming:javascript:javascript_notes [2007/03/13 16:54] – titles billh
+++ docs:programming:javascript:javascript_notes [2008/08/03 00:25] (current) – external edit 127.0.0.1
@@ Line 32: / Line 32: @@
   * IE uses document.all("elemID")
   * Older Netscape browsers used document.layers[elemID]
-  * A utility function to get the proper element reference, regardless of browser:<code html>
+  * A utility function to get the proper element reference, regardless of browser:<code javascript>
 function getElem(elemID){
 	if(document.all){
@@ Line 41: / Line 41: @@
 		return document.layers[elemID];
 	}
+}
+...before doing anything with the object, you can make sure you have a valid object like this:
+var elem = getElem("SomeElementId");
+if(elem){
+	// elem is valid, so proceed with code
 }
 </code>
+===== Commenting =====
+<code javascript>
+<SCRIPT language="JavaScript">
+<!-- This opens the HTML comments that will hide the script from old browsers
+// javascript comment
+......Javascript Statements.......
+/*
+multi-line
+javascript
+comment
+*/
+//--> This closes the comment section and the browser will read on normally
+</SCRIPT>
+</code>
+===== Linking to an external script file =====
+<code javascript>
+// in the <head> section of an html page
+<script type="JavaScript" src="scriptFilename.js"></script>
+</code>
+===== Testing for existence of a property or method =====
+<code javascript>
+if(elem && typeof elem.property != "undefined"){
+  // element property is valid - it is safe to use this property
+}
+if(elem && typeof elem.method != "undefined"){
+  // element method is valid - it is safe to call this method
+}
+</code>