JOI上调用的多个function如何工作？

Question

How does Joi.string().aphanum() and so on work. How is it possible to stack function calls one after the other like this, as shown in name and birthyear. Is this function all in a class or something and if it is how is this possible to chain of function calls like this

const Joi = require('joi'); 
const schema = Joi.object().keys({ 
  name: Joi.string().alphanum().min(3).max(30).required(),
  birthyear: Joi.number().integer().min(1970).max(2013), 
}); 

Answer 1

That's exactly right. Each of these methods return a new object (that also has those methods). It's very similar to doing something like someString.toUpperCase().split("") in normal Javascript. This will first get the string, run the built-in toUpperCase function on it, and then run another built-in function split on the returned string.

You're just stacking methods and building new objects after each call.

Its possible because each of these methods return the newly modified object.