Solved, See UPDATE below. You can use this code as reference to implement something simillar

Lets say I have a parent react component (ES6):

Parent

import ChildDiv from './ChildDiv'



export default React.createClass({

  displayName: 'ParentDiv',



  getInitialState () {

    nodesLoadedToCanvas: 0,

    workedOnParentOnceAfterAllChildrenWereLoaded: false

  },



  onChildNodeDidMount () {

    let nodeCount = this.state.nodesLoadedToCanvas + 1

    this.state.nodesLoadedToCanvas = nodeCount

    console.log('Mount ' + this.state.nodesLoadedToCanvas + ' nodes so far')

  },



  render () {

    const {children} = this.props // 'children' is a model collection



    return (

      <div id='ParentDiv'>

      {children.map((childDiv) => 

        <ChildDiv data={childDiv} key={childDiv.id} onRender={this.onChildNodeDidMount}/>

      )}

      </div>

    )

  },



  componentDidMount () {

    console.log('Parent did mount')

  },



  componentDidUpdate () {

    let allNodesArePresent = (this.state.nodesLoadedToCanvas === this.props.children.length)

    if (!this.state.workedOnParentOnceAfterAllChildrenWereLoaded) {

      console.log('Do something')

      this.state.workedOnParentOnceAfterAllChildrenWereLoaded= true

    }

  }

})

And a child-component like this

Child

export default React.createClass({

  displayName: 'ParentDiv',



  render () {

    const {data} = this.props



    return (

      <div id='ParentDiv'>

        data.name

      </div>

    )

  },



  componentDidMount () {

    console.log('ChildDiv did mount')

    this.props.onRender() // tell parent that child did mount

  },



  componentDidUpdate () {

  }

})

Why is my console saying

Parent did Mount

ChildDiv did Mount

ChildDiv did Mount

ChildDiv did Mount

And not

ChildDiv did Mount

ChildDiv did Mount

ChildDiv did Mount

Parent did Mount

?

How can I make react call a function after the full parent (and all it's childs) are rendered?

UPDATE

I solved this with the Input of @nash_ag by adding a onRender={this.onChildNodeDidMount} Parameter to my tag (see above), call the function in ChildDiv in componentDidMount() and can now decide if all nodes were loaded in my parents componentDidUpdate() method. I updated my code above.