Javascript async
Introduction
Typical Failing Code
export function raceCondition() {
let xhr = new XMLHttpRequest();
let statuses = [];
xhr.open("GET", "http://localhost:3000/ordersStatuses");
// Success
xhr.onload = () => {
statuses = JSON.parse(xhr.responseText);
};
let xhr2 = new XMLHttpRequest();
xhr2.open("GET", "http://localhost:3000/orders/1");
// Success
xhr2.onload = () => {
const order = JSON.parse(xhr2.responseText);
const description = status.map((t) => {
if (t.id === order.orderStatusId) {
return t.description;
}
})[0];
setText("Order Status: ${description}");
};
xhr2.send();
}
This may fail because it finishes the second request before the first. I.E. we did not wait for the first request before using the second request.