js return a promise

1function doSomething() {
2  return new Promise((resolve, reject) => {
3    console.log("It is done.");
4    // Succeed half of the time.
5    if (Math.random() > .5) {
6      resolve("SUCCESS")
7    } else {
8      reject("FAILURE")
9    }
10  })
11}
12
13const promise = doSomething(); 
14promise.then(successCallback, failureCallback);

1function myAsyncFunction(url) {
2  return new Promise((resolve, reject) => {
3    const xhr = new XMLHttpRequest();
4    xhr.open("GET", url);
5    xhr.onload = () => resolve(xhr.responseText);
6    xhr.onerror = () => reject(xhr.statusText);
7    xhr.send();
8  });
9}