React css transition does not work correctly

Question

I've written a React app, using CSS transitions. But those transitions does not work correctly in some of the components. In my app, only the components who are moving upwards works well, those who are moving downwards moves instantly without animation. (I want them both moves with animation.)

Here is the CSS I used there:

div.canvas {
    position: absolute;
    top: 90px;
    left: 60px;
    width: 640px;
    height: 480px;
    border: 1px solid #999;
    background: white;

}

div.canvas-rect {
    position: relative;
    margin-left: 20px;
    margin-top: 10px;
    height: 20px;
    background: green;

    transition: all 1s linear;
    -moz-transition: all 1s linear; /* Firefox 4 */
    -webkit-transition: all 1s linear; /* Safari 和 Chrome */
    -o-transition: all 1s linear; /* Opera */

}

UPDATED:

I also built a codepen.io project to show the problem. It has the complete code of this demo project.

I've tried to add a log entry to componentDidUpdate, componentDidMount and componentWillUnmount methods to show whether these component are re-created or updated, it shows that they are all updated (not re-created, or removed) every second.

user_3494439 · Answer

I know this wasn't the case, but since I got here also looking for React css transition does not work correctly, I just wanted to share:

If you create an element using arrow functions inside render, it won't get properly animated, since a new componente is always being created. You should create a function outside and invoke it in 'render'.

user_3294482 · Answer

You can trick React by using index as key. If you think about el, and index as starting position (index) and end position (el), the element has moved to the old end position by the end of the transition, and by when it's there, it's taken over by the new start position and (index) is switched to match the new setup. This is because when you set key in an element in react, the virtual DOM will always interpret it as it is the same element. And for the sake of it, you're right in setting index as the "id" in general.

I made a working example only by switching index/el (and setting element position to absolute).

const {combineReducers, createStore} = Redux;
const { Provider, connect } = ReactRedux;

const ArrList = ({
  arr
}) => (
  {
  arr.map((el, index)=>
          
            {el}
          ) }
  
)
      
const mapStateToArrList = (state) => {
  return {
    arr: state.appReducer.arr
  }
};

const App = connect(mapStateToArrList, null)(ArrList);

const initialState = {
  arr: [1, 2, 3, 4]
}

const appReducer = (state = initialState, action) => {
  switch(action.type) {
    case "tick":
      return {
        ...state,
        arr: _.shuffle(state.arr)
      }
    default:
      return state
   }
}

const reducer = combineReducers({
  appReducer
})


const store = createStore(reducer)

ReactDOM.render(
  
    
  ,
  document.getElementById('root')
)

const dispatcher = () => {
  store.dispatch({
     type: "tick"
  })
  setTimeout(dispatcher, 1000)
}

dispatcher()

.element {
    position: absolute;
    height: 20px;
    background: green;
    margin-left: 20px;
    margin-top: 20px;

    text-align: right;
    color: white;
    line-height: 20px;

    transition: all 1s ease-in;
    -moz-transition: all 1s ease-in; /* Firefox 4 */
    -webkit-transition: all 1s ease-in; /* Safari 和 Chrome */
    -o-transition: all 1s ease-in; /* Opera */

}

.element-1 {
    width: 20px;
}

.element-2 {
    width: 40px;
}

.element-3 {
    width: 60px;
}

.element-4 {
    width: 80px;
}

.index-1 {
  top: 20px;
}

.index-2 {
  top: 40px;
}

.index-3 {
  top: 60px;
}

.index-4 {
  top: 80px;
}

user_2553923 · Answer

You did recreate DOM elements each time.
You should define collect key value. I changed your key value '' + el to '' + index.

Just change css properties only :)

React css transition does not work correctly

5 Answers