this.state return empty array when render - react-native

Question

I wanted to display the array series and when I tried to console the array this.state.series in the function it does has the result and the value inside but when I render this.state.series just keep giving empty array. I wonder is it because of the componentDidMount()?
constructor(props){
super(props);
this.state={series:[]}
}
GetTransaction=()=> {
var APIURL="http://10.0.2.2:80/api/getTransaction.php";
var headers={
'Accept':'application/json',
'Content-Type':'application.json'
}
fetch(APIURL,
{
method:'POST',
headers: headers,
})
.then((response)=>response.json())
.then((response)=>
{
this.setState({results:response});
this.state.results[0].map((a) => {
this.state.series.push(a.count)
});
console.log(this.state.series)
})
.catch((error)=>
{
alert("Error"+error);
}
)
}
componentDidMount(){ // runs after the component output has been rendered to the DOM
this.GetTransaction();
}
render(){
console.log(this.state.series)
output
Array []
Array []
Array []
Array []
Array []
Array []
Array []
Array [
"1",
"2",
"1",
"1",
]

Answer 1

There are basically 2 errors in GetTransaction state assignment:
you can't read a state just assigned because this.setState is async. If you want to get the very last value of state you should use this.setState's callback:
this.setState({results:response}, () => {
console.log(this.state.result); //<-- here you have the very last value of result
});
state must be always setted with this.setState: this.state.series.push(a.count) is not good.
So you have to rewrite your code in this way:
...
this.setState({results:response}, () => {
let seriesAppo = [];
this.state.results[0].map((a) => {
seriesAppo.push(a.count);
});
this.setState({series: seriesAppo}, () => {
console.log(this.state.series);
})
});
...

Answer 2

That‘s weird
this.state.results[0].map((a) => {
this.state.series.push(a.count)
});
Don‘t manipulate state that way, only with setState.
const series = response[0];
this.setState({series: series});
Even if you wanna add elements to an array you have to recreate the array. You can achieve this as follows:
const series = response[0];
this.setState({series: […this.state.series, …series]});