The Command Line & Data Types

Wilson Espina

What did we do last lesson?

Learning Objectives

At the end of this class, you will be able to:

• Work with files/directories via the Terminal
• Introduce Git basic commands and distinguish Git from GitHub
• Run basic JavaScript code on the command line interface (CLI)
• Introduction to variables and primitive data types

Agenda

• Using the Terminal
• Git and GitHub
• Command Line JS
• Variables & Data types

Exit Ticket Questions

The Terminal

Javascript on the Command Line

• Terminal===Command Line===Console
• Terminal allows you to interact with your computer faster
• Lets you perform tasks that would be difficult through graphical user interface (GUI)

Shell

• A generic name for the primary program that runs inside a Terminal
• Common shell programs include:
• Bash (Bourne-Again Shell)
• ZSH (Z Shell)
• Powershell

BONUS: Type like a Hacker

Anatomy of the Terminal

SPACE

Anatomy of the Terminal

SPACE

Anatomy of the Terminal

SPACE

Anatomy of the Terminal

Command (program)

Anatomy of the Terminal

Flag or Option

Anatomy of the Terminal

Output

Introduction to Git / GitHub

Git

Git is distributed version control system

• Programmers use Git to keep the history of all the changes to their code
• This means that they can rollback changes (or switch to older versions) as far back in time as they started using Git on their project.

GitHub is for collaboration

• A hosting service for Git repositories
• A web interface to explore Git repositories
• Hosts files in the cloud.
• A social network of programmers
• We all have individual accounts and put our codebases on our GitHub account
• You can follow users and star your favorite projects

Local vs Remote

Local

• Repository on your own machine
• Similar to saving on MS Word

Remote

• Code is stored in the Cloud and is accessible by others
• Similar to saving on Google Drive

How We Will Use GitHub in JS9

jsd-9-resources

• contains start and solution files
• you will pull changes at the start of each lesson

jsd-9-homework

• you will push your completed homework and receive feedback here

• you will create additional repos for your own projects

Git Commands

git init
						

• Initiates a new local Git repository
• Creates a .git subdirectory in the current working directory

Git Commands

git add -A
git add .
						

Or for individual files

git add filename
						

• Adds or stages changes in the working directory to the files to be included in the commit snapshot.
• This snapshot is now stored in a temporary staging area which Git calls the "index".

Git Commands

git commit
git commit -m "Commit Message"
						

• Permanently stores the contents of the index in the repository.
• Commits the staged files to the project history as a snapshot.
• Also adds a timestamp and records who made the changes.

Git Commands

git branch newbranchname
git checkout -b newbranchname
						

• Makes a copy of the working directory in the current branch and allows you to make changes without affect the other branch.
• The git checkout –b command is a shortcut to create the branch and move into it.
• Use git checkout branchname, to return to an existing branch.

Git Workflow

Node js

Node.js

• Node.js is an open-source, cross-platform runtime environment for developing server-side Web applications.
• Interprets JS using Chrome's V8 engine
• Faster execution with non-blocking, asychronous input/output
• Written in C, C++, and JS (so, not a JS framework)

Levels of Abstraction

• 1's and 0's towards the bottom of the iceburg
• Human readable languages towards the top
• C++ is lower level
• JavaScript is a high level of abstraction from machine code

Node vs the Browser

What is Node used for

• Allows us to run JavaScript from our terminal applications
• Creating and running scripts
• File management
• Creating a backend server for a web application

Running Node in the Command Line

	> 3 + 4 // your command
	< 7 // Node's response
								

	> node /filepath/script.js
								

	> 7
								

JavaScript Variables

Variables

Containers for data that allow us to store values

• Allows our program to remember values for us to use later on
• The action of saving a value to a variable is called assignment
• Similar to putting information on a shelf

Naming Variables

• Use camelCase - first letter is lowercase and proceeding words are uppercase: anExampleOfCamelCase
• Names can only contain: letters, numbers, $ and _
• No dashes, no full stops and cannot start with a number
• Case sensitive - numberofbooks is not the same as numberOfBooks

When do you use console.log

• Used only during development to check what's going on
• Allows you to debug your code
• You can add multiple console.log's

Data Types

Primitive Data Types

Strings

let title = "star wars"

title.toUpperCase();
"STAR WARS"
							

Numbers

> 0.1 + 0.2
0.30000000000000004
							

Arithmetic Operators

The standard arithmetic operators are supported, including addition, subtraction & modulus (or remainder)

> 1 + 2;
3

> 2 - 5;
-3

> 5 / 2;
2.5

> 6 * 2;
12
						

Compound Operators

Modulus (%)

> 9 % 4
1
						

Special Number Operators

The Math object provides methods for additional operations

Math.pow(m,n)	// Returns m to the power of n
Math.sqrt(n)	// Returns the square root of n
Math.random()	// Returns a random number between 0 (inclusive) and 1 (exclusive)
Math.floor(n)	// Returns largest integer less than or equal to n
Math.ceil(n) 	// Returns smallest integer greater than or equal to n
						

Boolean

A Boolean value can either be true or false. Any value can be converted to a boolean value in JS

Learning Objectives - Review

• Work with files/directories via the Terminal
• Introduce Git basic commands and distinguish Git from GitHub
• Run basic JavaScript code on the command line interface (CLI)
• Introduction to variables and primitive data types

Look Ahead to Next Lesson

• Running JavaScript in the Browser
• Create arrays and access values in them
• Build iterative loops using for statements.
• Iterate over and manipulate values in an array.