Lesson 5: DOM Objects and Built-In Objects

Question 1

What is BOM (DOM)?

Answer 1

the Browser Object Model.

Question 2

What are two window methods?

Answer 2

alert() and prompt()

Question 3

What is returned if the user clicks the cancel button on a prompt popup?

Answer 3

Null value.

Question 4

What does confirm(“msg”) do?

Answer 4

Return true or false depending on which button is clicked on the popup.

Question 5

Show an example of confirm():

Answer 5

let answer = confirm("is 3+2=5?");
if (answer==true) (alert("correct"); }
else {alert("wrong"); }

Question 6

What does getElementBiId() do?

Answer 6

Returns a reference to an element with the id specified.

Question 7

Show an example of getElementById:

Answer 7

const h1 =
document.getElementById('title');

Question 8

What is innerHTML used for?

Answer 8

Setting or changing element content.

Question 9

What does the window.history object do?

Answer 9

Stores a list of the URLs previously visited using the current browser tab.

Question 10

What does the location object contain?

Answer 10

Information about the currently loaded page.

Question 11

What does the navigator object contain?

Answer 11

Data about the browser application.

Question 12

Math.abs(a):

Answer 12

Returns the absolute value of a.

Question 13

Math.celi(a):

Answer 13

Rounds a up to the next integer.

Question 14

Math.floor(5.8):

Answer 14

Rounds a down to the next integer.

Question 15

Math.round(a):

Answer 15

Rounds a to the nearest integer.

Question 16

Math.sqrt(a):

Answer 16

Returns the square root of a.

Question 17

Math.max():

Answer 17

Gets the max value of its arguments.

Question 18

Math.min():

Answer 18

Gets the min value of its arguments.

Question 19

Math.random():

Answer 19

Creates random numbers between 0 and 1.

Question 20

Show a display of a random integer between 1 and 10:

Answer 20

let randomNum = Math.floor((Math.random() * 10) + 1);
let el = document.getElementById('info');
el.innerHTML = '<h1>random number</h1><p>' + randomNum + '</p>';

Question 21

What does the keyword ‘with’ do?

Answer 21

Takes an object as an argument and is followed by a code block.

Question 22

Show an example using the ‘with’ keyword:

Answer 22

with (math) {
var myRand = random();
var biggest = max(3,4,5);
var height = round(76.35);
}

Question 23

Create a date object with today’s date:

Answer 23

let myDate = new Date();

Question 24

Other ways to create a Date object:

Answer 24

• new Date()
• new Date(year, month, day, hrs, mins, secs, milliseconds)
• new Date(milliseconds)
• new Date(date string)

Question 25

What does alert() do?

Answer 25

Pauses all user interaction with the page until the user clears the dialog.

Question 26

Show an example of alert()

Answer 26

alert(“this is my message!”);

Question 27

What does prompt() do?

Answer 27

Opens a modal dialog, allowing users to enter information.

Question 28

Show an example of a prompt():

Answer 28

var answer = prompt(“What is your name?”, “John Doe”);