Eloquent JavaScript

Free, Comprehensive, But Heavy on Math for Beginners

Eloquent JavaScript is available for free as a PDF or you can purchase it online. It was crowd funded by a group of people concerned there was a good modern resource covering topics for beginners. Here’s how to get it from the command line with curl:

curl -LO https://rwx.gg/reviews/books/eloqjs/eloqjs.pdf 

These annotations are incomplete at this time.

Introduction

• What what your favorite part?

Chapter 1

Chapter 2

Stuff to Find a Home For (in the Above)

Dangers of Number()

In the following Number() is not a cast (if you know what that is). It doesn’t force the string into being a number. Instead, it returns NaN if its argument is not a number. This then has to be checked to be sure that the string entered in response to the prompt() is actual a number and not something else.

For Loops with in Versus of

The old in operator iterates over the properties (usually the names) and not the values. This makes in do things that seem unexpected and is the reason of was added to ES6 (and that you should generally use it instead).

let list = [4, 5, 6]

  for (let i in list) {
     console.log(i) # NOT 4, 5, 6
  }

  for (let i of list) {
     console.log(i)
  }

0
  1
  2
  4
  5
  6

Here’s one that is even more unexpected:

let devices = new Set(["Linux", "Mac", "Windows"]);
  devices["category"] = "desktops"

  for (let device in devices) {
     console.log(device)
  }

  for (let device of devices) {
      console.log(device)
  }
  

category
  Linux
  Mac
  Windows