JavaScript

Question 1

create a dialouge box that says “Hello from Treehouse”

Answer 1

alert(“Hello from Treehouse”);

Question 2

print to the page “Welcome to JavaScript Basics”

Answer 2

document.write(“<h1> Welcome to JavaScript Basics </h1>”);

Question 3

add JavaScript to an HTML document

Question 4

link a scripts.js file to an html file

Question 5

print a “Start program” message to the console

Answer 5

console.log(“Start program”);

Question 6

create a dialogue box which displays the contents of the var message

Answer 6

alert(message);

Question 7

escape the apostrophe in She’s a great programmer.

Answer 7

She's a great programmer. (backslash is above Shift on the US keyboard)

Question 8

capture visitor’s input by storing prompt data in a visitorName variable

Answer 8

var visitorName = prompt(‘What is your name?’);

Question 9

create a var message that combines the greeting ‘Hello’ with the visitor’s name (var name) and “Welcome”;

Answer 9

var message = “Hello “ + visitor + “. Welcome”;

Question 10

concatenation operator

Answer 10

+=

Question 11

create a variable fullName which combines firstName and lastName

Answer 11

var fullName = firstName + “ “ + lastName;

Question 12

print to the console var message converted to upper case

Answer 12

console.log(message.toUpperCase());

Question 13

what is an integer?

Answer 13

a whole number without a decimal point (5, 10, etc.)

Question 14

convert var totalBadges = HTMLBadges + CSSBadges from string to numbers

Answer 14

var totalBadges = parseInt(HTMLBadges) + parseInt(CSSBadges);

Question 15

function for converting a string with integers to numbers

Answer 15

parseInt();

Question 16

convert ‘1.25’ to numbers

Answer 16

parseFloat(‘1.25’);

Question 17

round 4.5 to the nearest integer using a math method

Answer 17

Math.round(4.5);

Question 18

erase all the data from the console

Answer 18

clear();

Question 19

create a random number from 1 to 6 using Math.random

Answer 19

Math.floor(Math.random () * 6) +1;

Question 20

create a random number within a range from bottomNumber to topNumber

Answer 20

var randomNumber = Math.floor(Math.randon() * (topNumber - bottomNumber +1)) + bottomNumber;

Question 21

equality operator

Answer 21

===

Question 22

write a conditional statement that gives to alternatives 1) Yes, that’s right 2) Sorry, that’s wrong to a question ‘What programming language is the name of a gem?

Answer 22

var message = prompt(‘What programming language is the name of a gem?’);

if (answer.toUpperCase === ‘RUBY’) {
	document.write(<p>“That’s right” </p>)
} else {
	document.write(<p> Sorry. That’s wrong. </p>)
}

Question 23

single line comment

Answer 23

// This is a single line comment.

Question 24

multiple line comment

Answer 24

/* This is a multiple line code . . . 
. . . . */

Question 25

and operator

Answer 25

&& (two ampersands)

Question 26

or operator

Answer 26

|| (two pipes, just above shift)

Question 27

create a sayHi function with an alert that says Hi

Answer 27

``` function sayHi () { alert('Hi'); } ```

Question 28

call the sayHi function

Answer 28

sayHi();

Question 29

Which JavaScript keyword is used to send back a value from a function?

Answer 29

return

Question 30

if var age < 18 display an error message "You are too young to use this program".

Answer 30

``` if (age < 18) { throw new Error("You are too young to use this program"); } ```

Question 31

Finish the code below, so that the function returns the message variable: ``` function greeting( name ) { var message = "Hello " + name; ``` }

Answer 31

``` function greeting( name ) { var message = "Hello " + name; return message; } ```

Question 32

create an array myShopping and add 3 items to the lisst

Answer 32

var myShopping = ['milk', 'bread', 'butter'];

Question 33

print the first item of the myShopping array to the console

Answer 33

console.log(myShopping [0] );

Question 34

create a for loop that prints numbers from 1 to 10;

Answer 34

for (i=1, i<11, +=1) { console.log(i); }

Question 35

add numbers 7, 8 and 9 to the numbers array using the push method

Answer 35

numbers.push(7, 8, 9);

Question 36

add 5, 11, 12 to the beginning of the numbers array

Answer 36

numbers.unshift(5, 11, 12);

Question 37

Where do you normally put the js script tags inside an html document?

Answer 37

Just before the closing body tag

Question 38

print out the whole of myShopping array

Answer 38

printList (myShopping);

Question 39

remove the last item from the myShopping array

Answer 39

myShopping.pop( );

Question 40

remove the first item from the myShopping array

Answer 40

myShopping.shift( );

Question 41

find out how many items are inside the myShopping array

Answer 41

myShopping.length

Question 42

display the contents of the myShopping array inside the console

Answer 42

myShopping

Question 43

display the last used command in the console

Answer 43

press the up arrow on the keyboard

Question 44

remove the first item from the array myShopping and place it in the buyLater variable

Answer 44

var buyLater = myShopping.shift( );

Question 45

iterate through the students array and print the values to the console

Answer 45

var students = [‘Mike’, ‘Kate’, ‘Jane’, ‘Louis’]; for (var i = 0; i < students.length; +=1) { console.log(students[i]); }

Question 46

Use a while loop to iterate through the values in the temperatures array var temperatures = [100,90,99,80,70,65,30,10];

Answer 46

var temperatures = [100,90,99,80,70,65,30,10]; var i = 0; while (i < temperatures.length) { console.log(temperatures[i]); i += 1; }

Question 47

Use a for loop to iterate through the values in the temperatures array var temperatures = [100,90,99,80,70,65,30,10];

Answer 47

for (var i = 0; i < temperatures.length; i+=1) { console.log(temperatures[i]); }

Question 48

create a daysString variable that converts the daysInWeek array into a string with values separated by comma

Answer 48

var daysString = daysInWeek.join( ‘, ‘ );

Question 49

create a new array allStudents that joins currentStudents with newStudents arrays

Answer 49

var allStudents = currentStudents.concat(newStudents);

Question 50

save the index position of Apple in the new variable position var fruits = ['Apple', 'Orange', 'Grapefruit'];

Answer 50

var position = fruit.indexOf(‘Apple’);

Question 51

access the age property of the person object with an alert window

Answer 51

``` var person = { name: 'David', age: 24 } ``` alert(person.age);

Question 52

change the name property of the person object to 'Bobby'

Answer 52

``` var person = { name: 'David', age: 24 } ``` person.name = 'Bobby';

Question 53

add a new country property to the person object set to Brazil

Answer 53

``` var person = { name: 'David', age: 24 } ``` person.country = 'Brazil';

Question 54

create a function that prints a message inside an html div

Answer 54

``` function print(message) { var div = document.getElementbyId(‘output’); div.neerHTML = message; } ```

Question 55

loop through the keys of the student object and print them to the console

Answer 55

var student = { name: “Dave”, grades: [80, 85, 90, 95] }; for ( var propName in student ) { console.log(propName); }

Question 56

loop through the values of the student object and print them to the console

Answer 56

var student = { name: “Dave”, grades: [80, 85, 90, 95] }; for ( var propName in student ) { console.log(student[propName]); }

Question 57

print multiple variables in the console and separate them with a colon

Answer 57

console.log(variable1, ': ', variable2);

Question 58

what does JSON stand for?

Answer 58

JavaScript Object Notation