JavaScript: Promises

When code refers to a promise defined in another code block, the referencing code implicitly awaits the promise.

Most often, promises are used to load files, fetch data from a remote server, or query a database. TK Elaborate some more and give more specific examples of promises, including FileAttachment, fetch, db.sql, waiting to click on a button.

As a contrived example, within the block below, hello is a promise that resolves via setTimeout; if you reference hello from another code block or expression, the other code won’t run until the timeout fires and will see hello as a string.

const hello = new Promise((resolve) => {
  setTimeout(() => {
    resolve("hello");
  }, 1000);
});

Hello is: .