Week 2 - Conditionals and Functions

Object Basics

As discussed last week, when you create a variable and put something inside it, the thing that you are putting inside is either a Primitive value OR an Object.

JavaScript comes with lots of pre-built objects, but we can also create our own generic objects to hold any information we want. Here is a sample bit of JavaScript that creates an Object with four properties inside it.

let steve = {
  job: 'Professor',
  id: 123456,
  email: 'griffis@algonquincollege.com',
  alive: true,
};

Two of the property values hold String primitive values, one holds a number primitive value, and the last holds a Boolean primitive value.

Learn more about Object in JavaScript

Booleans

Booleans are one of the Primitive types. They can have a value of true or false. The value must be written in lowercase and have no quotation marks around it. However, other values in JavaScript will also be considered either truthy or falsy.

Learn about truthy and falsy

if Statements

When your program needs to make a decision and carry out different tasks based on the value of one or more variables, then an if statement is how we do this.

They are known as Control Flow statements. Here is a simple example:

let x = 123;
if (x < 100) {
  console.log('x is less than 100');
} else {
  console.log('x is more than or equal to 100');
}

Learn more about if statements

Ternary Statements

The ternary statement allows us to write simple logic statements similar to an if..else statement but one one line, with less syntax. Here is a simple example of one:

let y = x < 100 ? 50 : 150;
//y will be assigned either the value 50 or the value 150
//depending on the value of x.

Learn about ternary statments

Functions

In JavaScript, functions are a way to bundle together a series of commands so that they can be called all together at the same time. Here is an example of what a function declaration looks like.

function doSomething() {
  let num = Math.random(); //generate a random number between 0 and 0.99999999
  console.log(num);
}

doSomething(); //tell the  doSomething function to run

Learn more about functions

Scope and Hoisting

Scope is a term that describes the area in your code where each variable and function is visible to other parts of your code.

When variables and functions are declared, they are actually hoisted to the top of their scope. This is done before any of your code is executed.

Learn more about scope and hoisting

Future Video Reference

When trying to find one of Steve's videos on a certain topic, go to the Channel Home page Video Tab and click on the Search icon beside the About tab. You can type in the name of the video title or part of it.

Alternatively, you can go to the playlist page The videos are grouped by topic into playlists. Eg: Arrays, DOM, Events, Functions, etc.

Special Character Reference

Here is a list of the special characters that you will use in programming and what they are each called. Some have multiple names

: colon
; semi-colon
{ } curly braces
[ ] square-brackets
( ) parentheses
` backtick
' single quotes
" double quotes
< > angle brackets (less than, greater than)
! not operator or bang operator
& ampersand
# hashtag, pound sign, octothorpe
- dash, hyphen, subtraction operator
+ addition operator
* asterix, multiplication operator
% percentage sign, modulus operator
/ forward slash, division operator
\ back slash
_ underscore
~ tilde
, comma
. period, dot operator
? question mark
^ caret (pronounced like "Carrot")
@ at-sign
| pipe character, pipe operator

TODO

TODO Before next week

• If you have not read all these notes and watched the videos from this week, do that first.
• Finish and submit the exercises Exercise 1 - variables and Exercise 2 - objects this week, before 5pm on Tuesday.
  • Exercises page
• Complete Hybrid 4 - Websites before next Monday at 5pm.
  • Hybrid page
• Read ahead the notes for week 3 to prepare for class and the quiz.