Intro to JavaScript

RDU

Learn how to problem-solve using JavaScript
Practice programming fundamentals
Identify next steps for learning

Today's goals

Ben White
Left an anthropology PhD program after four years
Worked as a developer first in 2010 at a marketing software company doing sentiment analytics
Joined Thinkful in 2013 as an education engineer, and now run curriculum development

About me

First steps towards becoming a software engineer
Communicate better with developers
Build out your business and app ideas

Why learn JavaScript?

Details at http://githut.info

What is JavaScript?

Written by Brendan Eich in 1995
Initial version written in 10 daysFront end:
Unrelated to Java, but named to draft off its popularity
Default programming language of browsers.

What is JavaScript?

Programming language you can use to write instructions a computer can follow
Front end:
- Retrieve data from APIs and display it
- Handle user interactions
Server side:
- Create APIs
- Serve static resources
- Manage data and persistence
Rich community and eco-system of open source libraries

What is programming?

Using everyday language to clearly state a problem.
Using precise language to describe different solutions.
Implementing a solution to the problem in a way your computer can understand.

What we'll cover today

How to get JavaScript code to execute on a webpage.
How to use variables
How to use functions to create reusable sets of instructions
JavaScript's data types
Using Chrome Developer tools to write and execute JavaScript in the browser.

What we won't cover...

HTML and CSS
Server-side programming
jQuery or any JavaScript framework
Object oriented programming
etc.

Our starting point

Install Google Chrome if you don't have it already
Install Sublime Text 3 if you don't have a text editor you use
Download the starter files: https://github.com/Thinkful-Ed/intro-to-js-starter-files
Open starter files in Sublime Text
Open index.html in browser and Developer Tools

Our starting point

Project open in Sublime text
Page open in Chrome
Developer tools open (Mac: option-cmd-J, windows: Ctrl + Shift + J

Working with variables

A variable is a name that points to a value.

Shorthand way to refer to values we create elsewhere in a program.
Allow us to manage state in a program.

Working with variables

JS bin here

Syntax for variables

Declaring vs. assigning vs. declaring and assigning

// declaring
var firstVariable;

// assigning a value
firstVariable = 6;


// re-assigning value
firstVariable += 1;

// referring to variable
console.log(firstVariable);
alert(firstVariable);


// declaring and assigning
var secondVariable = 'foo';

Syntax for variables

Use the var keyword
Assign a value with the assignment (=) operator
Semi-colons after each line of code

Naming variables

Choose meaningful words for variable names. numberOfGorillas is better than x
Use camelCasing. First word starts with lowercase, subsequent words with uppercase.
Must start with a letter.

What kinds of values can variables have?

String
Number
Function
Object
Null
Undefined
Boolean

Strings

Create with opening and closing quotes (single or double)
Can concatentate them

var foo = 'foo';
var bar = "bar";
var fooBar = foo + bar;

Numbers

Can represent integers and floating point decimals
Can use arithmetic operators to manipulate (aka, +, -, *, /)

var width = 10;
var height = 5.5;
console.log("Area is " + (width * height)); // => Area is 55

Booleans, undefined, null

Booleans signify truth or falsity
`null` is special value indicating variable has no value
`undefined` is special value browser assigns to declared but unassigned variables. Never directly set a variable's value to `undefined`.

// booleans and logical operators
var sunny = true;
var warm = false;
var shouldGoOut = sunny && warm;

// null
var accountNum = null;

// undefined
var myVar;
console.log(myVar);

Functions

Used to represent re-usable sets of instructions

// defining 
function sayHi() {
  console.log('Hi');
}

// executing
sayHi(); // => Hi


// this function takes a `name` argument
function sayHiToName(name) {
  console.log('Hi ' + name);
}

sayHiToName('Sheila') // => Hi Sheila

// this function *returns* a value
function isEven(num) {
 return num % 2 === 0;
}

isEven(3); // => false

Objects

Hold collections of values together

// defining object
var fido = {
  type: 'dog',
  legs: 4,
  name: 'Fido',
  speak: function() { console.log('arf arf') }
};

// dot notation
console.log(fido.name) // => Fido
fido.speak(); // => arf arf

// reassigning the value of .legs
fido.legs = 3;

// bracket notation
fido['type']; // => dog


// arrays
var myList = [1, 2, "three", true, fido];
myList[0]; // => 0

Challenge 1: Say your name

Remove existing code from `app.js`
Add a new function called `sayMyName`
This function should log the text `My name is Ben`, displaying your name in place of Ben
Define the function, and then call it
Consider using Dev Tools to interactively code solution
Save changes to `app.js`
Should be able to see output in Dev Tools

Solution 1: Say your name

// inside app.js

function sayMyName() {
  console.log('Ben');
}

sayMyName();

Challenge 2: Write an adder function

Add new code below existing code in `app.js`
Create new function called `adder`.
`adder` should take two arguments: `num1` and `num2`
It should return the value of num1 + num2
Define the function, and then call it
Save changes to `app.js`
Should be able to see output in Dev Tools

Solution 2: Write an adder function

// inside app.js

// ... existing code

function adder(num1, num2) {
  return num1 + num2;
}

console.log(adder(3, 5));

Deeper into strings

Built in string methods

var foo = "foo bar foo bar foo bar";
foo.length; // =>
foo.charAt(0); // => "f"
foo.indexOf("bar"); // => 4
foo.slice(1); // => "oo bar foo bar foo bar"
foo.split(" ") // => ["foo", "bar", "foo", "bar", "foo", "bar"]
foo.toUppercase() // => "FOO BAR FOO BAR FOO BAR"
foo.replace('foo', 'bar') // => 'bar bar bar bar bar bar'

Deeper into strings

Special characters and escaping

var foo = "He said, \"Foo!\"";
var bar = 'Dear Paul,\nHow are you?';

Challenge 3: wiseperson function

Add new code below existing code in `app.js`
Create new function called `wisePerson`.
`wisePerson` should take two arguments: `who` and `what`
Given inputs of "Paul" for `who` and "Carpe diem!" for `what`, `wisePerson` should print the string value "A wise person named Paul said: 'Carpe diem!'"
Define the function, and then call it
Save changes to `app.js`
Should be able to see output in Dev Tools

Solution 3: wiseperson function

function wisePerson(who, what) {
 console.log(
  "A wise person named " + who + " said, '" +
  what + "'");
}

wisePerson('Paul', "Carpe diem!");

Challenge 4: Shouter

Add new code below existing code in `app.js`
Create new function called `shouter`.
`shouter` should take one `text`, which is a string.
It should return the text in all uppercase

console.log(shouter(
  "I am whispering can't you tell?")); // => I AM WHISPERING CAN'T YOU TELL?

Solution: Shouter

function shouter(text) {
  return text.toUpperCase();
}

console.log(shouter('I am whispering'));

Challenge 5: Tweet analyzer

Add new code below existing code in `app.js`
Create new function called `analyzeTweet`.
Paste the code from this gist: http://bit.ly/2gCzPNO
`analyzeTweet` should take one arguments: `tweet`, which is an object representing a tweet
Be aware that this challenge is more difficult than the previous ones. Use it as an opportunity to work at the edge of your comfort zone.

{
 text: "All your base belong to us",
 author: "haxor3000",
 wordLength: 5,
 isRetweet: false,
 mentionsOthers: false
}

Challenge 5: Tweet analyzer

Given:

{
 text: "All your base belong to us",
 author: "haxor3000",
 wordLength: 5,
 mentionsOthers: false
}

var tweet = {
  author: "@billy",
  text: "All your base belong to us"
  id: 333333
}

`analyzeTweet(tweet)` should return:

Challenge 5: Tweet analyzer

Given:

{
 text: "RT @billy all your base belong to us",
 author: "@sally",
 wordLength: 8,
 mentionsOthers: true
}

var tweet = {
  author: "@sally",
  text: "RT @billy All your base belong to us"
  id: 444
}

`analyzeTweet(tweet)` should return:

Challenge 5: Tweet analyzer

Hints

// convert string into array of words

var foo = ['lions and tigers and bears oh my!']
var splitUp = foo.split(" ");
console.log(splitUp); // => [
  'lions', 'and', 'tigers', 'and', 'bears', 'oh', 'my'];

// get length of array

var myArray = [1, 2, 3];
console.log(myArray.length); // => 3


// check if string contains substring
var string = "cats and dogs"
var containsCats = string.indexOf("cats") > -1;

Solution: Tweet analyzer

function analyzeTweet(tweet) {
  return {
   text: tweet.text,
   numberWords: tweet.split(" ").length,
   mentionsOthers: tweet.indexOf('@') > -1
  };
} 

analyzeTweet({
    text: 'lions and tigers and bears',
    author: '@janeDoe',
    id: 2020202020
});

Next steps for learning

Spend your first 10 hours on Codecademy
Google is your friend
Find an app idea you're excited about and practice at the edge of your abilities
Learn about jQuery and DOM manipulation
Structured learning:
- Free / cheap online resources
- Night classes at community college
- Coding bootcamp (on or off line)
Ignore the "flavor of the month" (for now).

Thank you!

Email me with questions or suggestions:

ben@thinkful.com

RDU