What does the function then mean in JavaScript

Question

I've seen code that looks like this:

myObj.doSome("task").then(function(env) {
    // logic
});

Where does the function then() come from?

Answer 1

The then() method is similar to "Javascript promises," which are utilised in libraries or frameworks such as jQuery or AngularJS.

A promise is a design pattern for dealing with asynchronous actions.

The promise allows you to utilise a method named "then" to define which function(s) to use as callbacks.