Modules

Question 1

What is the module specification used by Node.js initially?

Answer 1

CommonJS

Question 2

Why don’t browsers support CommonJS?

Answer 2

CommonJS loads modules synchronously.

Question 3

When you use CommonJS, what bindings are available so it can interact with other modules? What do they do?

Answer 3

require: a function that makes sure a module is loaded and returns its interface.

exports: an object which is the interface object for the module. It starts out empty and you add properties to it to defined exported values.

Question 4

Can require only be used at the top-level, or can it be used in functions too?

Answer 4

Since require is a normal function it can be used anywhere.

Question 5

How do you declare your dependencies with CommonJS?

Answer 5

Call require like this:

const ordinal = require("ordinal");

Question 6

How do declare your interface in CommonJS?

Answer 6

Use exports or module.exports.

module.exports = { foo: "bar" };

Question 7

What’s are two differences between a regular script and a ES module?

Answer 7

Regular scripts have bindings defined in the global scope and have no way to directly reference other scripts.

Modules get their own separate scope and support the import/export keywords to declare their dependencies and interface.

Question 8

How to define an interface with ES modules?

Answer 8

The export keyword can be put in front of a function, class, or binding definition.

export function doWork() { 
    return 7; 
}

Question 9

In ES Modules, how do you make the bindings from another module available in the current module?

Answer 9

The import keyword

import { dayName } from "./dayname.js";

Question 10

What is the default keyword used for in ES Modules?

Answer 10

Often used for modules that export a single binding.

export default ["Winter", "Spring", "Summer", "Autumn"];

This binding can be imported without the braces around the variable name.

import seasonNames from "./seasonname.js";

Question 11

How do you import all bindings from a module at the same time using ES Modules?

Answer 11

Use import *. You provide a name, and that name will be bound to an object holding all the module’s exports.

import * as dayName from "./dayname.js";
console.log(dayName.dayName(3));