Post, split props ReactJs - reactjs

Question

I would like to explain my problem of the day.
this is the part of the code that works
here I recovered 2 data "title" and "quantity" here it works very well
postbackend = () => {
const newItems = this.props.items.map((item) => {
const { title, quantity, } = item;
return {
title,
quantity,
};
});
const config = {
method: "POST",
headers: {
"Content-Type": "application/json",
};
body: JSON.stringify({ ...this.state, items: newItems,
};
const url = entrypoint + "/alluserpls";
fetch(url, config)
.then(res => res.json())
.then(res => {
if (res.error) {
alert(res.error);
this.props.history.replace("/OrderSummaryPaymentFalseScreen"); // Your Error Page
} else {
alert(`film ajouté avec l'ID ${res}!`);
this.props.history.push("/OderSummaryScreen"); // Your Success Page
}
}).catch(e => {
console.error(e);
this.props.history.replace("/OrderSummaryPaymentFalseScreen"); // Your Error Page
}).finally(() => this.setState({
redirect: true
}));
so i tried this ,and I would like to separate "title" and "quantity".
example like this
const newItems = this.props.items.map((item) => {
const { title } = item;
return {
title,
};
});
const newQuantity = this.props.items.map((item) => {
const { quantity } = item;
return {
quantity,
};
});
const config = {
method: "POST",
headers: {
"Content-Type": "application/json",
},
body: JSON.stringify({ ...this.state, items: newItems, quantityforproduct: newQuantity,
};
but it doesn't work
Do you have an idea of how to fix this? Neff