@workInProgress
@ngdoc overview
@name Developer Guide: Angular HTML Compiler: Widgets: Creating Custom Widgets
@description

When you create your own widgets, you must set up your own namespace for them.  (See
dev_guide.bootstrap Initializing Angular} for information about namespaces in angular.)

Let's say we would like to create a new element type in the namespace `my` that can watch an
expression and `alert()` the user with each new value:

<pre>
// An element widget
<my:watch exp="name"></my:watch>
</pre>

You can implement `my:watch` like this:

<pre>
angular.widget('my:watch', function(compileElement) {
 var compiler = this;
 var exp = compileElement.attr('exp');
 return function(linkElement) {
   var currentScope = this;
   currentScope.$watch(exp, function(value){
     alert(value);
   });
 };
});
</pre>


# Creating a Custom Attribute Widget

Let's implement the same widget as in the example in Defining an Element Widget, but this time as
an attribute that can be added to any existing DOM element:

<pre>
// An attribute widget (my:watch) in a div tag
<div my:watch="name">text</div>
</pre>
You can implement `my:watch` attribute like this:
<pre>
angular.widget('@my:watch', function(expression, compileElement) {
  var compiler = this;
  return function(linkElement) {
    var currentScope = this;
    currentScope.$watch(expression, function(value) {
      alert(value);
    });
  };
});
</pre>


# Live Example of a Custom Element Widget

<doc:example>
<doc:source>
<script>
angular.widget('my:time', function(compileElement){
  compileElement.css('display', 'block');
  return function(linkElement){
    function update(){
      linkElement.text('Current time is: ' + new Date());
      setTimeout(update, 1000);
    }
    update();
  };
});
</script>
<my:time></my:time>
</doc:source>
<doc:scenario>
</doc:scenario>
</doc:example>


# Additional Compiler Methods for Custom Widgets

The angular compiler exposes methods that you may need to use of when writing your own widgets and
directives.  For example, the `descend()` method lets you control whether the compiler ignores or
processes child elements of the element it is compiling.  For information on this and other
compiler methods, see the {@link api/angular.compile Compiler API doc}.


## Related Topics

* {@link dev_guide.compiler Angular HTML Compiler}
* {@link dev_guide.compiler.directives Angular Directives}
* {@link dev_guide.compiler.widgets Angular Widgets}
* {@link dev_guide.compiler.directives.creating_directives Creating Custom Directives}

## Related API

* {@link api/angular.compile Compiler API}
