JavaScript Midterm

*What is the difference between HTML, CSS and JavaScript?*

HTML=structure/framework

CSS=design

JavaScript=interactive features

*How does the computer interpret the world through code?*

Uses a model of an object; object-oriented programing

*Describe objects:*

\*objects are things:

\-they have properties, events, and methods

\-properties+events+methods=object

*Describe events:*

\*involve user interactions

\-programmers choose what events trigger a specific section of code

\-scripts can trigger different types of functionality

*Describe methods:* 

\*how people interact with objects

\-second part of the code after period (member operator)

Identify the event and method

document.write(‘Good afternoon!’)

\
   event                 method

|------------| |-----------------------------|

document.write(‘Good afternoon!’)

*Describe how computers interpret the code:*

Events trigger methods and methods retrieve or update an objects properties

Describe variables

store temporary bits of information to perform a task

Identify the variable and name

var boldColor | let boldColor

variable name

|----| |---------|

var boldColor

what are the variable keywords?

var

let

const

how do you declare a variable?

give it a name (identifier)

describe value

data that is stored within the variable

a value must be assigned to a variable

What are the different data types?

Numeric, strings, boolean

Describe the numeric data types

can be decimals or negative numbers

cannot have commas

describe strings

consist of letters and characters

add content to a page

always within ‘single’ or “double” quotation marks

describe booleans

can only have 1 of 2 values, true or false

describe arrays

a special type of variable that stores a list of values

what are the characteristics of an array

always in \[square brackets\] or array()

used for a list or set of values, useful if the number of items will vary

always separated by commas, uses ‘single’ or “double” quotes

index starts with 0

ex:

let stopLight;

stopLight = \[‘yield’, ‘stop’, ‘walk’\];

stopLight\[1\] = ‘go’

describe what is happening in this script

ex:

let stopLight;

stopLight = \[‘yield’, ‘stop’, ‘walk’\];

stopLight\[1\] = ‘go’

stopLight has an index of 1 which would be stop, but it is set equal to go, so stop is being changed to go making the stopLight array \[‘yield’, ’go’, ‘walk’\]

describe expressions

result in a single value

describe operators

used to create a single value from one or more values

what are the 4 different operators?

assignment (=)

string (+)

logical (&&)

comparison (> |

what is the assignment operator

=

assigns a value to a variable

what is the string operator

\+

combines two strings

what is the logical operator

&&

combines expressions as true or false (boolean)

what is the comparison operator

> <

compares values

explain this script

describe functions

a series of statements that are grouped to perform a task

describe conditions

conditions determine a path to take

returns a true or false value (boolean)

describe conditional statements

if a condition is met, then a statement is executed

else code executes a different statement (AKA code skips ahead)

if statements compares value to true

else if the value is false

describe the DOM

document object model

views and changes the output of HTML without actually changing the original HTML

what is the entry node of the DOM tree?

document node