1// Sinxron — yuqoridan pastga ketma-ket
2console.log("1");
3console.log("2");
4console.log("3");
5// 1, 2, 3
6
7// Asinxron — kutish bor
8console.log("1");
9setTimeout(() => console.log("2"), 1000);
10console.log("3");
11// 1, 3, 2   ← 2 keyin chiqadi

1setTimeout(() => {
2  console.log("3 sekund o'tdi");
3}, 3000);
4
5// Custom callback
6function malumotOl(callback) {
7  setTimeout(() => {
8    const data = { ism: "Ali", yosh: 17 };
9    callback(data);
10  }, 1000);
11}
12
13malumotOl((natija) => {
14  console.log("Keldi:", natija);
15});

1userOl(id, (user) => {
2  postlarniOl(user.id, (postlar) => {
3    kommentOl(postlar[0].id, (kommentlar) => {
4      javobOl(kommentlar[0].id, (javoblar) => {
5        // ...chuqur va chuqur...
6        console.log(javoblar);
7      });
8    });
9  });
10});

1const vada = new Promise((resolve, reject) => {
2  setTimeout(() => {
3    const muvaffaq = Math.random() > 0.3;
4    if (muvaffaq) {
5      resolve("Ma'lumot keldi");
6    } else {
7      reject("Xato yuz berdi");
8    }
9  }, 1000);
10});
11
12vada
13  .then((natija) => console.log("OK:", natija))
14  .catch((xato) => console.log("Xato:", xato))
15  .finally(() => console.log("Yakun"));
16
17// Ketma-ket zanjir
18fetch("/api/user")
19  .then(res => res.json())
20  .then(user => fetch("/api/posts/" + user.id))
21  .then(res => res.json())
22  .then(posts => console.log(posts))
23  .catch(err => console.error(err));

1// Then bilan
2function userOl() {
3  return fetch("/api/user")
4    .then(res => res.json())
5    .then(user => console.log(user));
6}
7
8// async/await bilan (ancha toza)
9async function userOl() {
10  const res = await fetch("/api/user");
11  const user = await res.json();
12  console.log(user);
13}

1async function malumotOl() {
2  try {
3    const res = await fetch("/api/user");
4    if (!res.ok) throw new Error("Status: " + res.status);
5    const user = await res.json();
6    return user;
7  } catch (err) {
8    console.error("Xato:", err.message);
9    return null;
10  }
11}

1// GET so'rov
2async function postlariOl() {
3  const res = await fetch("https://jsonplaceholder.typicode.com/posts");
4  const postlar = await res.json();
5  return postlar.slice(0, 5);
6}
7
8// POST so'rov
9async function yangiPost(sarlavha, matn) {
10  const res = await fetch("https://jsonplaceholder.typicode.com/posts", {
11    method: "POST",
12    headers: { "Content-Type": "application/json" },
13    body: JSON.stringify({ title: sarlavha, body: matn }),
14  });
15  return await res.json();
16}
17
18// Promise.all — parallel
19async function koplabOl() {
20  const [users, posts] = await Promise.all([
21    fetch("/api/users").then(r => r.json()),
22    fetch("/api/posts").then(r => r.json()),
23  ]);
24  return { users, posts };
25}