JavaScript

Question 1

scripts

Answer 1

programs that accompany web pages.

Run in web browsers and make web pages more dynamic and powerful

Question 2

variables

Answer 2

should start with lower case letter

Question 3

displays in browser console

Answer 3

console.log()

Question 4

displays on the web page

Answer 4

document.write()

Question 5

mark the end of a statement

Answer 5

semicolon

optional unless we write multiple statements in a single line

Question 6

comments

Answer 6

// single line
/*multi
line*/

Question 7

open the console

Answer 7

Ctrl + Shift + J

Question 8

javascript

Answer 8

programming language of the web

Question 9

create a variable

Answer 9

var name/identifier = value;

Question 10

undefined

Answer 10

a value

Question 11

maximum number of decimal places JavaScript can handle

Answer 11

17

Question 12

to know what type of data a variable contains

Answer 12

console.log(typeof(variable’s name));

Question 13

data types

Answer 13

string
numbers
Boolean
object

Question 14

special kind of comparison operator that requires the value and the type to be equal

Answer 14

===

Question 15

logical and

logical or

Answer 15

&&

||

Question 16

assign a value to a variable based on a condition being true or false

Answer 16

conditional operator

?

Question 17

if non-boolean values have real value except 0, “”, undefined

Answer 17

when converted condition returns true

Question 18

perform different actions based on different condition

Answer 18

conditional statements

if, switch

Question 19

concatenate strings

Answer 19

string.concat(string);

Question 20

to find how many characters a string have

Answer 20

string.length;

Question 21

escaping character

Answer 21

\

Question 22

extract a piece of string

Answer 22

slice(start, end);

substr(start, length);

Question 23

replace

Answer 23

string.replace(search string, replace string);

Question 24

change a string to use lower/upper case letters

Answer 24

string. toLowerCase();

string. toUpperCase():

Question 25

multiplication and devision with a non-numeric string result in

Answer 25

NaN
not a number
but its type is number

Question 26

casting

Answer 26

parstInt(string);

parseFloat(string);

Question 27

round a number

Answer 27

Math.round(number);

Question 28

Math.random();

Answer 28

produces a random number between 0 and 1

Question 29

Date

Answer 29

date.getFullYear();
date.getMonth();
date.getDate();
date.getDay(); returns week day as a number from 0 to 6
toDateString();

Question 30

special kind of variable that contains several values of a type or even different types

Answer 30

array
great way to store related values
var array_name = [content];

Question 31

[ ]

Answer 31

array litteral

Question 32

turns an array into a comma-separated string

Answer 32

array. toString();

array. join();

Question 33

a property that keeps track of number of values in the array

Answer 33

length

Question 34

create arrays from strings

Answer 34

string.split(separator);

Question 35

add values at the end of an array

Answer 35

array.push(value);

Question 36

removes the last value from array

Answer 36

array.pop();

Question 37

remove a value from the beginning of an array

Answer 37

array.shift();

Question 38

add a value at the beginning of an array

Answer 38

array.unshift(value);

can use with multiple values

Question 39

a method that can add, insert, replace and remove values

Answer 39

array.splice(index, how many values we want to remove, optional value to be added at the index);

Question 40

sort an array

Answer 40

in alphabetical order - array.sort();

reverse order - array.sort().reverse();

Question 41

for loop

Answer 41

for(control_variable; condition; increment){statement;}

Question 42

enhanced for loop

Answer 42

suppose thing is an array

for (var thing in things){……}

Question 43

do while loop

Answer 43

runs at least one, even if the condition is false

Question 44

skip specific iteration but continue loop

Answer 44

continue

Question 45

find if a word ends with something

Answer 45

string.endsWith(“text”);

Question 46

sample function definition

Answer 46

function sayHello(){console.log(“Hello!”);}

Question 47

variables that contain several values or properties

Answer 47

objects

Question 48

object literal

Answer 48

{ }

Question 49

sample object

Answer 49

var person = {name:”Kajan”, age:22, height:1.62};

Question 50

if we want to get rid of a property

Answer 50

delete object.key;

Question 51

defining a method

Answer 51

speak : function(){………}

Question 52

use ……….. keyword to create as many instances of the object as we want

Answer 52

new

Question 53

javascript can be placed in the …………. and the …………. sections of an HTML page

Answer 53

body

head

Question 54

javascript display possibilites

Answer 54

writing into an alert box
writing into an HTML output
writing into an HTML element
writing into the browser console

Question 55

writing into an alert box

Answer 55

window.alert()

Question 56

writing into an HTML output

Answer 56

document.write()

Question 57

writing into an HTML element

Answer 57

using innerHTML

Question 58

writing into the browser console

Answer 58

console.log()

Question 59

javascript increases the speed by

Answer 59

validating user inputs before sending to the server and also reducing the load on the server

Question 60

JavaScript code is written inside ………… of the html file
you need to set the ………… attribute of the script to ……………

Answer 60

script tag
type
“text/javascript”

Question 61

variables in javascript are declared using …….. keyword

Answer 61

var

Question 62

in Javascript it is not required to specify the type of value a variable is going to hold

Answer 62

javascript itself takes care of it

Question 63

variable name should start with

Answer 63

alphabet or underscore

cannot begin with numbers

Question 64

javascript variables are ……………..

Answer 64

case sensitive

Question 65

scope of javascript variable can be …………. or ………….

Answer 65

local

global

Question 66

a website might be just static content

Answer 66

web app would have dynamic content

Question 67

the way javascript sees its containing pages’ data

Answer 67

DOM - Document Object Model

Question 68

render

Answer 68

to draw

Question 69

display a message box with an OK button

Answer 69

alert()

Question 70

display a message box which prompts for some user input

Answer 70

prompt(text, default_text)

Question 71

display a dialog box with a message, ok and cancel button

Answer 71

confirm()

returns true if the user clicked ok

Question 72

return true if the value and type of two variables are not equal

Answer 72

!==

Question 73

conditional or ternary operators

Answer 73

checks a condition and based on the condition evaluates the value of a variable
?

Question 74

bitwise and(&)

Answer 74

perform boolean AND operation on each bit of its variable

Question 75

bitwise or

Answer 75

|

Question 76

bitwise xor

Question 77

bitwise not

Answer 77

~

Question 78

left shift(<>)

Answer 78

to shift all bits in the first operand to left by the number of bits in the right operand

Question 79

check whether a particular property is present within an object

Answer 79

in operator

Question 80

check whether an object is an instance of the specified object

Answer 80

instanceof