Angular ng-click event delegation

Question

So if i have a ul with 100 li's should there be ng-clicks in each li or is there a way to bind the event to the ul and delegate it to the li's kind of what jquery does? Would this be better or worse? Are we having 100 events or is it just one event in the end?

Answer 1

It seems angular doesn't do event delegation with repeaters. Someone opened an issue on github about it. The argument is if it actually leads to better performance.

There might be a workaround but it would require jQuery. It consists of creating a special directive to be used on a parent element and register the listener on its dom node.

Here's an example, that is passed a function name to be called when a children node is clicked, and is also passed a selector to help identify which children nodes to listen to. Since angular's jquery implementation only gives us the bind method - which is limited to registering event listeners to the actual element - we need to load jQuery to have access to either the on or delegate method.

HTML

<ul click-children='fun' selector='li'>
    <li ng-repeat="s in ss" data-index="{{$index}}">{{s}}</li>
</ul>

The function defined is defined in the controller and it expects to be passed an index

$scope.fun = function(index){
    console.log('hi from controller', index, $scope.ss[index]);      
};

The directive uses $parse to convert an expression into a function that will be called from the event listener.

app.directive('clickChildren', function($parse){
  return {
    restrict: 'A',
    link: function(scope, element, attrs){       
      var selector = attrs.selector;
      var fun = $parse(attrs.clickChildren);   
      element.on('click', selector, function(e){       
        // no need to create a jQuery object to get the attribute 
        var idx = e.target.getAttribute('data-index');        
        fun(scope)(idx);        
      });
    }
  };
});

Plunker: http://plnkr.co/edit/yWCLvRSLCeshuw4j58JV?p=preview

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Note: Functions can be delegated to directives using isolate scopes {fun: '&'}, which is worth a look, but this increases complexity.