Introduction to Javascript

Question 1

Javascript runs…

Answer 1

on the browser rather than the server. Whereas before in order to perform action, data and operations were being sent to the server.

Question 2

Javascript is an _____ programming language

Answer 2

interpreted

Question 3

Javascript Alerts

Answer 3

alert(“Text to Display Alert”);

Question 4

JS Data Types

Answer 4

Different Types
String
Boolean
Number

Question 5

typeof()

Answer 5

Output of function
“number”
“boolean”
“string”

Question 6

JS Variables

Answer 6

prompt(“Dialogue to display for prompt”);
To declare a variable use, var.
var, variables can later be changed to a different value
Example:
var myName = “Anand”;

Question 7

Naming and Naming Conventions for JS Variables

Answer 7

Variable names cannot start with a number

Variable can only contain numbers, letters, $, and/or _

Question 8

Variables follow a camel-case format.

Answer 8

First word contains lowercase, then subsequent words contain capital letters for their names

Question 9

String Concatenation

Answer 9

Can combine strings using +
Example:
“Hello” + “World” -> “HelloWorld”

Question 10

String Lengths and Retrieving the Number of Characters

Answer 10

To check the number of characters in a string

stringVariable.length

Question 11

Slicing and Extracting Parts of a String

Answer 11

Slice Function
stringslice(x, y);
Slices the string from x to y. Including x, up to but not including y
Example:
“Anand”.slice(0,3);
“Ana”

Question 12

Changing Casing in Text

Answer 12

toUpperCase()
Example:
“word”.toUpperCase()
“WORD”
toLowerCase()

Question 13

Basic Arithmetic and the Modulo Operator in Javascript

Answer 13

Modulo
%
Gives the remainder of a division
Example:
9 % 6 = 3

Question 14

Increment and Decrement Expressions

Answer 14

x++
x = x + 1;
x- -
x = x - 1;

Question 15

Creating and Calling Functions

Answer 15

Declaring functions:
function myFunction() { <code> }
Calling a function
myFunction();</code>

Question 16

Function Parameters and Arguments

Answer 16

Example:
function getMilk(money) { … }

Question 17

Function Outputs and Return Values

Answer 17

Include a return statement in the function to make it a function that has an output

Question 18

Control Statements: If-Else Conditionals and Logic

Answer 18

if ( condition ) { < code to run, if condition is true > }

else { < code to run, if condition is false> }

Question 19

Comparators and Equality

Answer 19

===
Is equal to
Checks both for the value and the data types
!==
Is not equal to
>, =
==
Only checks if the values equate to each other.
Doesn’t take into account the data types
So, 1 == “1”, will be equal to true

Question 20

Combining Comparators

Answer 20

&& 
AND
|| 
OR
!
NOT

Question 21

Javascript Arrays

Answer 21

Creating an array
Example:
Empty Array
var names = [];
Prefilling an array with elements
var names = [“Bob”, “John”, “Jennifer”];
Retrieving an element from an array
Example:
names[1]; // “John”
Array elements always start at 0
Retrieving the number of elements in an array
Array.length // Return the number of elements
Checking if an array contains a specific element
Array.includes(  );
Returns a boolean

Question 22

Adding Elements and Intermediate Array Techniques

Answer 22

Adding an element at the end of an array
Array.push( );
Remove and retrieve the last element of an array
Array.pop(); // Returns the last element of the array

Question 23

While Loops

Answer 23

while ( ) { // Code to run }

Question 24

For Loops

Answer 24

for(startingCondition ; conditionToRunLoopIfTrue; conditionModifier) { // Code to run if condition is true}
Example:
for(i = 0; i < 100; i++) { // Run code}