JS Async Promise

1_findUser.js

findUser(1)
    .then(function(user) {
        console.log("user:", user);
    });

function findUser(id) {
    return new Promise(function (resolve) {
        setTimeout(function() {
            console.log("waited 0.1 sec.");
            const user = {
              id: id,
              name: "User" + id,
              email: id + "@test.com"
            };
            resolve(user);
          }, 100);
    });
}

2_devide.js

function devide(numA, numB) {
    return new Promise((resolve, reject) => {
        if (numB === 0)
            reject(new Error("Unable to devide by 0."));
        else
            resolve(numA / numB);
    });
}

devide(8, 2)
    .then(result => console.log("성공:", result))
    .catch(error => console.log("실패:", error));
    
devide(8, 0)
    .then(result => console.log("성공:", result))
    .catch(error => console.log("실패:", error));

3_1_fetch.js

fetch('https://jsonplaceholder.typicode.com/posts/1')
  .then(response => console.log("response:", response))
  .catch(error => console.log("error:", error));

3_2_fetch.js

fetch()
  .then(response => console.log("response:", response))
  .catch(error => console.log("error:", error));

3_3_fetch.js

fetch('https://jsonplaceholder.typicode.com/posts/1')
  .then(response => response.json())
  .then(post => console.log("post:", post))
  .catch(error => console.log("error:", error));

3_4_fetch.js

fetch("https://jsonplaceholder.typicode.com/posts/1")
  .then(response => response.json())
  .then(post => post.userId)
  .then(userId => "https://jsonplaceholder.typicode.com/users/" + userId)
  .then(url => fetch(url))
  .then(response => response.json())
  .then(user => console.log("user:", user))
  .catch(error => console.log("error:", error));