How to call function after fetch() has finished

Question

I am using react-native and I have fetch GET request which takes an array. Now I need this fetch() to finish getting that array so I can call a function which will handle this array and do something with it. How do I wait for it to finish?
This is my request:

 componentWillMount(){ console.log("will mount"); fetch('SOME_API', { method: "GET", headers: { Accept: 'text/javascript', 'Content-Type': 'text/javascript', } }).then(response => response.json()).then(responseJson => { this.setState(function (prevState, props) { return {questions: responseJson, loading: false} }) }) }

And when this get request puts responseJson in state I want to call my function that will do something with that array.

If you need any more info please comment.

Thanks!

Answer 1

Just Define the function inside the class and call the function using this.{function_name} as below.

myFunction(responseJson) {
  // ... Your code ...
}
componentWillMount() {
  console.log("will mount");
  fetch(baseUrl + 'api/Customer/GetCustomerAccount/' + value, {
    method: 'GET',
  })
  .then((response) => response.json())
  .then((responseJson) => {
    this.myFunction(responseJson);
  })
}

Answer 2

Put an if statement in your render function:

 render(){

    if(this.state.loading){
        return(
            <View style={{flex: 1, padding: 20}}>
                // Your code if fetch() still fetching
            </View>
        )
     }

    return(
        <View style={{flex: 1, paddingTop:20}}>
            // Your code if fetch() has ended
            // the complete fetched data is this.state.questions
        </View>
    );
} 

Answer 3

I added another.then at the end and put the function inside it. In my case, I wanted to log the data received by fetch:

fetch(url).then(some function).then(function(){
    console.log(fetchResultData)
})