Reactjs - this.state.data.map arguments is UNDEFINED - node.js

Question

ive been trying to fetch data from my api but its somehow confusing that this.state.Data.map does work but the argument dynamicdata is undefined.
in App.js react
class ShowAll extends Component {
constructor(props){
super(props);
this.state = {
Data: [],
}
}
componentDidMount(){
Request.get('/budget').then((res)=>{
let DataString = JSON.stringify(res.body);
this.setState({
Data: DataString
}, function(){
console.log(DataString);
})
}).catch((err)=> console.log(err));
}
render(){
return(
<div>
{
this.state.Data.map(function(dynamicData, key){
<div>{dynamicData[0]._id}</div> // doesn't render anything and throws an error message saying TypeError: Cannot read property '_id' of undefined
})
}
</div>
)
}
}
**EDIT 1 **
The api data structure is
[{
"_id":"lul",
"_creator":"5a8f8ecdd67afa6494805bef",
"firstItem":"hero",
"secondItem":"30",
"thirdItem":"3",
"__v":0,
"tBudget":9,
"thirdPrice":3,
"secondPrice":3,
"firstPrice":3
}]

Answer 1

Oh. Your original post was a completely different problem.
Two problems. First:
You're mapping, so you don't need to index the mapped value
this.state.Data.map(function(dynamicData, n) {
// dynamicData _is_ the nth element in the array, you don't need dynamicData[x]
dynamicData._id === "lul"
})
second, you're not returning anything from your map callback
map(function(...) {
return (<div>...</div>)
})

Answer 2

Based on the server response, you don't need to access the item 0 when rendering each one of them
class ShowAll extends Component {
constructor(props){
super(props);
this.state = {
Data: [],
}
}
componentDidMount(){
Request.get('/budget').then((res)=>{
this.setState({
Data: res.body, // Assuming res.body is already an array
}, function(){
console.log(DataString);
})
}).catch((err)=> console.log(err));
}
render(){
return(
<div>
{
this.state.Data.map((dynamicData, key) => // Using an arrow function
<div>{dynamicData._id}</div> // Don't access the item 0
)
}
</div>
)
}
}
The previous code assumes res.body is already an array. If that's not the case and you are actually getting a string or something else, you need to parse the response and make sure you assign an array to the state.