prototype: Add Element#identify, which returns the element's ID if it exists, or sets and returns a unique, auto-generated ID (of the form 'anonymous_element_' + auto-incremented digit) otherwise. Use this when you need to ensure an element has an ID. Closes #9012.

CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Add Element#identify, which returns the element's ID if it exists, or sets and returns a unique, auto-generated ID (of the form "anonymous_element_" + auto-incremented digit) otherwise.  Use this when you need to ensure an element has an ID.  Closes #9012.  [Jeff Watkins, sam, Tobie Langel]
+
 * Make Element#readAttribute work for cloned elements in IE. Closes #8481. [chem, Tobie Langel]
 
 * Template enhancements.  Closes #8166.  [Christophe Porteneuve]

src/dom.js

@@ -233,6 +233,15 @@ Element.Methods = {
     return Selector.findChildElements(element.parentNode, args).without(element);
   },
   
+  identify: function(element) {
+    element = $(element);
+    var id = element.readAttribute('id'), self = arguments.callee;
+    if (id) return id;
+    do { id = 'anonymous_element_' + self.counter++ } while ($(id));
+    element.writeAttribute('id', id);
+    return id;
+  },
+  
   readAttribute: function(element, name) {
     element = $(element);
     if (Prototype.Browser.IE) {
@@ -597,7 +606,7 @@ Element.Methods = {
   }
 };
 
-Element.Methods.getElementsBySelector = Element.Methods.select;
+Element.Methods.identify.counter = 1;
 
 if (!document.getElementsByClassName) document.getElementsByClassName = function(instanceMethods){
   function isArray(className) {
@@ -636,6 +645,7 @@ if (!document.getElementsByClassName) document.getElementsByClassName = function
 }(Element.Methods);
 
 Object.extend(Element.Methods, {
+  getElementsBySelector: Element.Methods.select,
   childElements: Element.Methods.immediateDescendants
 });
 

test/unit/dom.html

@@ -342,6 +342,13 @@
 <div id="inlineAbsoluted" style="position: absolute"></div>
 
 <div id="unextended"></div>
+<div id="identification">
+  <div id="predefined_id"></div>
+  <div></div>
+  <div></div>
+  <div></div>
+  <div id="anonymous_element_3"></div>
+</div>
 
 <!-- Tests follow -->
 <script type="text/javascript" language="javascript" charset="utf-8">
@@ -676,6 +683,14 @@
         assert(element != $('intended'));
       });
     }},
+    
+    testElementIdentify: function() {with(this) {
+      var parent = $('identification');
+      assertEqual(parent.down().identify(), 'predefined_id');
+      assertEqual(parent.down(1).identify(), 'anonymous_element_1');
+      assertEqual(parent.down(2).identify(), 'anonymous_element_2');
+      assertEqual(parent.down(3).identify(), 'anonymous_element_4');
+    }},
        
     testElementClassNameMethod: function() {with(this) {
       var testClassNames = $('container').getElementsByClassName('test');