Code 102: Class 06 - JavaScript

Read: JavaScript and jQuery Pages 43-69

HTML, CSS, and JavaScript the three languages of a website

HTML <html> provides the structure and content of a web page
CSS {css} styles the webpage and defines how the content is displayed
JS javascript() controls how the page behaves
Attempt to maintain a separate file for each layer as much as possible
Progressive Enhancement popular approach to building web pages, each layer improves on the one before it

JavaScript plain text language so it does not require any additional tools to start

Objects and Methods

document.write('Good afternoon!');

document = Object the document object represents the entire page
. = Member Operator
write('Good afternoon!') = Method allows new content to be written into the page where the <script> element sits
'Good afternoon!' = Parameters whenever a method requires some info to work, data is given inside the parentheses

JavaScript runs where it is found in the html, location maters.

Chrome Developer Tools Shortcuts

Script set of step by step instrucitons that a computer can follow, each should end with a ;

JS is case sensitive
{} indicate the begining and ending of a code block
Statements instructions, each one should begin on a new line and end with a ;
Multiple statements can be grouped together between {} to form a singular related code block
/*comment*/ Format for a multiline comment
//comment Format for a single line comment
Variable location where scripts store data

Variables

Must declare a variable before being able to use it
- Example = var quantity;
- var = Variable Keyword
- quantity; = Variable Name sometimes called an identifier
  - If more than one word, typically written in camelCase: oneTwoThreeFour
Assign a value
- Example = quantity = 3;
- quantity = Variable name
- = = Assignment operator
- 3 = Variable value

Data Types

Numeric Data Types	String Data Types	Boolean Data Types
Example = `0.75`	Example = `'Hi, Ivy!'`	Example = `true`
For tasks involving counting or sums	Enclosed in a pair of single or double quotes used for working with text	True / False

Strings must always be surrounded by quotes either "string" or 'string' but not a combination. It must also be on one line.

6 Rules for naming variables

Computers take in information, stores info, processes it, and outputs calculation resutls.

Data and Binary

Bit is the smallest amount of information it stores either a 1 or a 0
Binary system only have two digits: 0 and 1
Text in binary each letter is assigned a number which is then represented by multiple bits

Circuits and Logic

All computer calculations are the result of many small and simple calculations performe useing logic in the hardware circuits

Memory, CPU, Input, and Output

Computers take input from the world, place it in memory, use the CPU to analyze or modify it, return it to memory, and output back to the user

Hardware and Software

Hardware are the physical components that make up computer
Software is the code that controls the hardware
CPU central processing unit
- Master chip of the system, has smaller dediated hardware inside for specific task, but its primary job is to determine which components to use when depending on the task at hand
Operating system master software of the system
- Program that controls all other programs and apportions inputs, resources, and outputs