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  Introduction

In this chapter you'll learn a completely new programming language: Javascript. While many developers use Javascript for all three layers of an application (data/persistence, logic, and presentation), in this camp we'll mostly be using Ruby for logic and data and often both Ruby and Javascript elements for presentation. During this week, we will use Javascript for both logic and presentation.

Javascript and Ruby (and most programming languages) have a lot in common. They both have variables, functions, arrays, and hashes. And thousands of other matching structures. But in many cases these are used slightly differently amongst languages. For instance, in Ruby a variable is declared like so:

age = 32

In Javascript:

let age = 32;

Functions look very different. In Ruby:

def foo(a, b)
  a + b
end

In Javascript we'll typically want to store a function inside a variable:

let fn = function foo(a,b){
  return a + b;
}

The following pages will give you a huge list of Javascript variables to play with. Open up any browser (we suggest Chrome), click "Inspect" and click "Console". Then you can put in any Javascript code - just like in IRB in the terminal.

A FEW NOTES ABOUT JAVASCRIPT
  • As we said above, it runs in the browser and not in the terminal. That may not mean much to you now, but keep it in mind.
  • Debugging does not take place with pry but with debugger;. It works in a similar way, pausing the code. You don't have to install anything.
  • Javascript is very unforgiving. In Ruby you can skip spaces, parentheses, etc. If you forget an end it will probably tell you expected tEND. Javascript isn't like that. You have to be very careful about your commas, colons, parentheses, curly brackets, and everything else. Every line in Javascript should end with a ;.