data.chinahighlights.com/js/autoemail.js

$(function() {
	var availableTags = [
		"@gmail.com",
		"@msn.com",
		"@hotmail.com",
		"@aol.com",
		"@yahoo.com"
	];
	function split( val ) {
		return val.split( /@\s*/ );
	}
	function extractLast( term ) {
		return split( term ).pop();
	}

	$( ".autoemail" )
		.bind( "keydown", function( event ) {
			if ( event.keyCode === $.ui.keyCode.TAB &&
					$( this ).data( "autocomplete" ).menu.active ) {
				event.preventDefault();
			}
		})
		.autocomplete({
			minLength: 0,
			source: function( request, response ) {
				response( $.ui.autocomplete.filter(
					availableTags, extractLast( request.term ) ) );
			},
			focus: function() {
				return false;
			},
			select: function( event, ui ) {
				var terms = split( this.value );
				terms.pop();
				terms.push( ui.item.value );
				terms.push( "" );
				this.value = terms.join( "" );
				return false;
			}
		});
});