javascript - Is my React component being recreated instead of updating? - Stack Overflow

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I am trying to bine Angular and React.js. I have an work example project here I have seen a couple of ways to bring the Angular and React.js together. One of the methods I have seen is to create a directive and create the React ponent in the link function. For example in the first part of the project to generate the React version(in red) I am using

.directive('reactElementRepeater', function() {
    return {
      link: function(scope, element) {
        var update_react = function(oldVal, newVal){ //Called every time one of the two values change
          React.renderComponent(Demo_Element({
            numberOfElements: scope.myModel.numberOfElem, 
            numberInElements: scope.myModel.numberInElem
          }), element[0]);
        }
        scope.$watch('myModel.numberOfElem.length', update_react);
        scope.$watch('myModel.numberInElem', update_react);
      }
    }
  });

What I want and what should happen in a React enabled application is for something in the model to be updated, then that update is sent through React and it will alter the DOM as little as possible to reflect that change. It looks like that instead of updating a bit of the DOM this will Create a new React ponent each time with renderComponent.

React.renderComponent() instantiates the root ponent, starts the framework, and injects the markup into a raw DOM element, provided as the second argument.

Is it actually recreating the elements each time? If that is the case is there a way to alter this so that doesn't happen? Just to be clear I know about ngReact, I just want to know other ways to speed up Angular with React.

I am trying to bine Angular and React.js. I have an work example project here I have seen a couple of ways to bring the Angular and React.js together. One of the methods I have seen is to create a directive and create the React ponent in the link function. For example in the first part of the project to generate the React version(in red) I am using

.directive('reactElementRepeater', function() {
    return {
      link: function(scope, element) {
        var update_react = function(oldVal, newVal){ //Called every time one of the two values change
          React.renderComponent(Demo_Element({
            numberOfElements: scope.myModel.numberOfElem, 
            numberInElements: scope.myModel.numberInElem
          }), element[0]);
        }
        scope.$watch('myModel.numberOfElem.length', update_react);
        scope.$watch('myModel.numberInElem', update_react);
      }
    }
  });

What I want and what should happen in a React enabled application is for something in the model to be updated, then that update is sent through React and it will alter the DOM as little as possible to reflect that change. It looks like that instead of updating a bit of the DOM this will Create a new React ponent each time with renderComponent.

React.renderComponent() instantiates the root ponent, starts the framework, and injects the markup into a raw DOM element, provided as the second argument.

Is it actually recreating the elements each time? If that is the case is there a way to alter this so that doesn't happen? Just to be clear I know about ngReact, I just want to know other ways to speed up Angular with React.

• javascript
• angularjs
• angularjs-directive
• reactjs

Share Improve this question Follow edited Jun 25, 2014 at 12:27 EasilyBaffled asked Jun 25, 2014 at 12:21 EasilyBaffledEasilyBaffled 3,8821010 gold badges5555 silver badges9292 bronze badges 1

• Its better late than never.. Out of curiosity I have to ask, why would you like to use ReactJS and AngularJS together? – refaelio Commented Mar 14, 2016 at 8:44

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1 Answer 1

Sorted by: Reset to default 10

Yes this is fine, it's not mounting the ponent multiple times.

When you call React.renderComponent() the second argument is the element which react should render the ponent to. So react notices if you are rendering the same ponent to a dom element that already contains a mounted instance of the ponent, and does not re-mount the entire ponent, it just updates the properties of it instead.

You can see this in action if you make a ponent with ponentDidMount function defined. You'll notice that ponentDidMount will only execute the first time renderComponent gets called. And afterwards, subsequent calls to renderComponent on the same target dom element will not call it because the ponent is already mounted. Likewise getDefaultState and getDefaultProps also only get called on the first renderComponent call.

If you're asking will the render function of the ponent be called every time the answer is yes. But this is how react works, you want the render function to get called because props might have changed. You can block it from being called by using shouldComponentUpdate (http://facebook.github.io/react/docs/ponent-specs.html#updating-shouldponentupdate) and returning false. However react developers remend you don't use this to block render calls unless you have specific performance problems - most of the time it should be fine to just let the render call execute as it wont cause any slow dom updates unless things have actually changed.

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