CGS 3066 - Exam 2, Javascript Questions and Answers Solved Correctly

CGS 3066 - Exam 2, Javascript Questions and Answers Solved Correctly

How to embed Javascript in HTML - Answers <script> tag

<script src="filename.js"></script>

How Javascript is executed - Answers Script file executed from top to bottom and run by the browser

for-loops - Answers for (let i = 0; i < 5; i++) { ... }

while-loops - Answers while (notFinished) { ... }

Conditionals - Answers If statements

if (...) {

...

} else {

...

}

Writing a function - Answers function name( ) {

statement;

statement;

...

}

Calling a function - Answers name( );

Variables in Javascript - Answers var, let, const

Always use const or let

var - Answers Function scope variable, same as let but dated

let - Answers Block scope variable

const - Answers Block scope constant, can't be reassigned

Function scope variable - Answers Only go out of scope at the end of functions so you can refer to the
same variable after the block has ended (after the loop or if-statement in which they are declared)

Block scope variable - Answers Can only be referred to within block (in the same brackets)

, Value types of variables - Answers Boolean, number, string, symbol, null, undefined, *object

Boolean type variables - Answers True or False, use && (and) || (or) ! (negation)



Example.

let isTeenager = age > 12 && age < 20;

age = 15;

isTeenager = true

String type variables - Answers Anything in single or double quotes

Null type variables - Answers Value meaning "this has no value"

Undefined type variables - Answers The value of a variable with no value assigned

Arrays - Answers Object types used to create lists of data, 0-based indexing, can check size via length
property



Example.

let list = [ ]; //creates empty list

let groceries = ['milk', 'cocoa puffs'];

groceries [1] = 'kix'; //changes cocoa puffs to kix



let first5 = [1,2,3,4,5]

console.log(first5[3]); //prints 4

Event-driven programming - Answers Code doesn't run right away but executes after some event fires
(click, hover, key, etc.)

Event Handler - Answers Any function listening to an event that executes when it occurs

Event Listener - Answers Tells function to run when event occurs



addEventListener(event name, function name);