Javascript

Question 1

D3: A good way to visualize binned data is

Answer 1

as shapes.

Question 2

D3: The three most popular D3 libraries are

Answer 2

dimple.js, Rickshaw, NVD3

Question 3

D3: The best D3 library for time series or streaming data is

Answer 3

Rickshaw

Question 4

D3: The DOM gets created during

Answer 4

page load

Question 5

Javascript: To clear the javascript console, type

Answer 5

clear()

Question 6

Javascript: In the javascript console, to return the html of the current page that has a certain css id, type

Answer 6

document.getElementById(“cssid”)

Question 7

Javascript: In the javascript console, to return the html of the current page that has a any css selector, type

Answer 7

document.querySelector(“.css-class”)

Question 8

D3: To select elements using D3, type

Answer 8

d3.select(“.css-class”)

Question 9

D3: To select a DOM element and then change its css styled color, type

Answer 9

d3.select(“.css-class”).style(“background-color”, “green”)

Question 10

D3: To check if the element you are selecting is unique, you can type

Answer 10

d3.selectAll(“.css-class”)

and then make sure the array returned has one item.

Question 11

D3: To select a DOM element and then change its text, type

Answer 11

d3.select(“.css-class”).text(“New Text”)

Question 12

D3: To select an element within your current selection, type

Answer 12

current_selection_var.select(“.inner-class”)

Question 13

D3: To change an html attribute, type

Answer 13

d3.select(“.css-class”).attr(“attribute_name”, “new value”)

Question 14

javascript: To set a string to uppercase, type

Answer 14

string_var.toUpperCase()

Question 15

javascript: To create a function, type

Answer 15

function fuctionName() {
}

Question 16

javascript: To create an anonymous function, type

Answer 16

var functionVar = function () {
};

note: requires semicolon

Question 17

javascript: To create a function that returns a string, type

Answer 17

function fuctionName() {
    return "string"
}

Question 18

jQuery: To hide an html element with the class=”class”, type

Answer 18

jQuery(“.class”).hide();

Question 19

jQuery: To show an html element with the class=”class” slowly, type

Answer 19

jQuery(“.class”).show(“slow”);

Question 20

jQuery: The abbreviation for jQuery is

Answer 20

$

Question 21

jQuery: Most jQuery methods return

Answer 21

the item selected, which allows for method chaining.

Question 22

javascript: To return all of the html tags of the body of a page, type

Answer 22

document.body.children

Question 23

javascript: To return all of the html tags on a page with a certain class name, type

Answer 23

document.getElementByClassName(“class”)

Question 24

jQuery: In the jQuery docs, animations are categorized as

Answer 24

Effects

Question 25

jQuery: To run a function when the DOM loads, type

Answer 25

$(document).ready(myFunction)
or
$(myFunction)

Question 26

jQuery: When manipulating the DOM using javascript it is a best practice to

Answer 26

not create a script that runs on ready and just add your script at the bottom of the body and assume it is ready.

Question 27

jQuery: To add html to an html element based on it’s class, type

Answer 27

$(“.class”).append(“-button>String-/button>”)

Question 28

jQuery: To remove the code for the precise button you are clicking, type

Answer 28

$(“button”).click(function() {
$(this).remove();
});

Question 29

jQuery: To traverse to the previous sibling page element before the element you selected by class, type

Answer 29

$(“.class”).prev()

Question 30

jQuery: To prevent a link from taking you to the next page, type

Answer 30

$(“a”).click(function(event) {
event.preventDefault();
})

Question 31

jQuery: To return the href of the link you just clicked, type

Answer 31

$("a").click(function() {
var my_attribute = $(this).attr("href");
})

Question 32

jQuery: To turn a string into a jQuery representation of a page element, type

Answer 32

var $my_element = $(-div>-/div>)

Question 33

jQuery: To signify that a variable is a jQuery object, people ofter

Answer 33

add a $ to the beginning of the variable name

Question 34

jQuery: The append method appends to

Answer 34

the end but still inside the tags you point at.

Question 35

jQuery: To use attr() to add an attribute to an element, type

Answer 35

$(“.class”)attr(“key”, “value”);

Question 36

jQuery: To append text into a tag, type

Answer 36

$(“.class”).text(“string”)

Question 37

ajax was originally called

Answer 37

xml http requestobject

Question 38

ajax: To make a web page know that it will work with ajax, add to the head

Answer 38

-script>
var xhr_object = new XMLHttpRequest();
-/script>

Question 39

ajax: a good response has the readyState value of

Answer 39

4

Question 40

ajax: the servers response is held in an attribute called

Answer 40

xhr_object.responseText

Question 41

ajax: To create a button that triggers the send method of an xhr_object, type

Answer 41

function sendAjax () {
    xhr_object.send()
}

-button onClick=”sendAjax()”>String-/button>

Question 42

ajax: The steps to use ajax are

Answer 42

create an xhr_object
set a response function
open the request
send the request

Question 43

ajax can only send requests to

Answer 43

one server

Question 44

ajax: To overcome ajax’s one host policy you can

Answer 44

have your server call the additional servers.

Question 45

ajax: To get images, css files and javascript files from an additional server, you can use

Answer 45

jsonp

Question 46

javascript: To go to a different url, type

Answer 46

window.location.replace(“http://www.google.com”);

Question 47

javascript: To return the url (including query string) of the current page, type

Answer 47

window.location.href

Question 48

javascript: to slice a string, type

Answer 48

string_var.slice(1,5);

Question 49

javascript: To return the index of a string, type

Answer 49

string_var.indexOf(“substring”);

Question 50

javascript: To make a div immediately scroll itself to the bottom, type

Answer 50

document.getElementById(‘div-id’).scrollTop = document.getElementById(‘div-id’).scrollHeight;

Question 51

javascript: To return the query string (including the “?”), type

Answer 51

window.location.search

Question 52

AJAX: long polling is

Answer 52

When the client sends a request to the server and the server makes the client wait until an event occurs before sending the data back, and then the client makes another long request.

Question 53

jQuery: To run a function upon every mouse movement, type

Answer 53

$(window).mousemove(function(event) {
console.log(event.type)
});

Question 54

jQuery: To run a function when the mouse leaves the window, type

Answer 54

$(document).mouseleave(function(){
console.log(‘string’)
})

Question 55

jQuery: To set or update a css property for a class, type

Answer 55

$(“.css-class”).css( “property”, “value”)

Question 56

jQuery: To effectively remove a css property, type

Answer 56

$(“.css-class”).css(“property”, “”)

Question 57

javascript: To set a cookie on the browser, type

Answer 57

document.cookie=”key=a value; expires=Thu, 01 Jan 2016 12:00:00 UTC; path=/”;

Question 58

javascript: To delete a cookie

Answer 58

update it with an expiration date that is in the past.

Question 59

javascript: To return the cookies on the browser, type

Answer 59

document.cookie;

Question 60

javascript: To save the return of a confirm box into a var, type

Answer 60

var confirm_var = confirm(“Accept or Cancel?”);

Question 61

javascript: The return of a confirm box is

Answer 61

accept: true
cancel: false

Question 62

ajax: each different type of ajax request you plan to make should

Answer 62

have its own xhr_object

Question 63

ajax: The xhr_object attribute that contains the state of the request, e.g. 4 if the response has arrived, is

Answer 63

xhr_object.readystate

Question 64

javascript: To change the html that is within an element, type

Answer 64

document.getElementById(“id”).innerHTML = “new html”

Question 65

ajax: All the code necessary to send and receive an ajax request is

Answer 65

var xhr_object = new XMLHttpRequest();
xhr_object.onreadystatechange = function() {
if (xhr_object.readystate === 4) {
document.getElementById("id").innerHTML =       xhr_object.reponseText;
}};

xhr_object.open(“GET”, “/endpoint?key=value”)
xhr_object.send();

Question 66

jQuery: To send an ajax request and then inject it into a page element using jquery, type

Answer 66

function functionName() {
$(".css-class").load("/endpoint?key=value");
};

Question 67

javascript: At the end of if statements. do not put

Answer 67

semicolon

Question 68

javascript: User inputs that are numbers must be converted from

Answer 68

string to integer.

Question 69

javascript: The “equal to” operator for javascript conditional statements is

Answer 69

===

Question 70

javascript: To create a conditional statement, type

Answer 70

if (4 === 4) {
document.write(“Equal”);
}

Question 71

javascript: To create an if else clause, type

Answer 71

if (my_int === 4) {
    document.write("Equal");
} else {
    document.write("Not Equal");
}

Question 72

javascript: strict equality operators (===) do not

Answer 72

convert a string to a number.

== does

Question 73

javascript: The scrict not equals operator is

Answer 73

!==

Question 74

javascript: Boolean values in javascript are

Answer 74

written in lower case. eg. false, true

Question 75

javascript: An “else if” statement is written as

Answer 75

if () {
} else if () {
}

Question 76

javascript: To use two conditional statements, use

Answer 76

double ampersand

Question 77

javascript: To create a single line comment in a javascript file, type

Answer 77

//

Question 78

bower is a

Answer 78

front end package manager that allows you to easily download from one place.

Question 79

node: To print an error to the console, type

Answer 79

console.error(errorMessage);

Question 80

node: A callback function is

Answer 80

the function that executes when a response to a request is received.

Question 81

Javascript: To erase whatever is in the browser console, type

Answer 81

clear()

Question 82

Javascript: To return a rounded number from a float, type

Answer 82

Math.round(2.2)

Question 83

ajax: To send an ajax request for the next page of django’s pagination every time a user scrolls to the bottom, type

Answer 83

var is_active = false
var page_num = 1
$(window).scroll(function() {
   if(!is_active && $(window).scrollTop() + $(window).height() + 100 > $(document).height()) {
      $.get('http://endpoint.com?page=' + page_num, function(data){ 
      $(".gallery").append(data)
       is_active = false
        page_num += 1
       });
   }
});

Question 84

jQuery: jQuery selectors select matching elements that

Answer 84

exist in the DOM when the code is executed, and don’t dynamically update.

Question 85

jQuery: in order to keep dom objects selected even after the initial jQuery execution, (e.g. when loading new objects from ajax), you can use

Answer 85

$(document).on(“click”, “.css-class”, function() {

});

Question 86

maps: To render a map

Answer 86

import maps api before body end
-script src=”https://maps.googleapis.com/maps/api/js?key=API_KEY&callback=initMap” async defer>

create container div

<div></div>

var map;
function initMap() {
  var map = new google.maps.Map(document.getElementById('map'), mapOptions);
}

Note: must add mapOptions json to the initMap function before the map var

Question 87

maps: To get the coordinates of a device, type

Answer 87

navigator.geolocation.getCurrentPosition(success);

Question 88

maps: the success callback function of navigator.geolocation.getCurrentPosition(success); should start with

Answer 88

function success(pos) {
  var crd = pos.coords;
  var lat = crd.latitude;
  var lng = crd.longitude;
}

Question 89

javascript: To write code that will only execute after a set amount of time, type

Answer 89

setTimeout(function(){
console.log(“string”)
}, 2000);

note: this is 2 seconds

Question 90

ajax: To create an ajax request using $.get, type

Answer 90

$.get(‘http://endpoint.com?key=value’, function(data){
console.log(data);
});

Question 91

javascript: To turn an int into a string, type

Answer 91

var num = 15;
var n = num.toString();

Question 92

javascript: To simulate a button click, type

Answer 92

document.getElementsByTagName(‘button’)[0].click();

Question 93

javascript: When you use window.location.replace(“http://url.com”)

Answer 93

it does not let the user return to the original page

Question 94

maps: To disallow dragging, type

Answer 94

var mapOptions = {
    draggable: false,
  }

Question 95

maps: to create a marker, type

Answer 95

var marker = new google.maps.Marker({
  position: {lat: 11.111, lng: 22.222},
  map: map,
  title: 'String'
});

Question 96

jquery: To create a function that executes immediately, type

Answer 96

$(function() {

});

Question 97

javascript: To reload a window, type

Answer 97

location.reload();

Question 98

maps: To get all the data to the browser you should

Answer 98

send it all in json and then unpack it with javascript, rather than try to server side render

Question 99

maps: To make a marker with a new icon image, type

Answer 99

var marker = new google.maps.Marker({
  position: myLatLng,
  map: map,
  icon: 'http://cdn.com/file.png'
});

Question 100

ajax: get generic ajax loading gifs with a transparent background at

Answer 100

www.ajaxload.info/

Question 101

ajax: To make an ajax loading symbol come up

Answer 101

add a gif image to the bottom of the page display:none; and when you send the ajax request, set it to initial, and then back to none in the callback function

Question 102

javascript: To make a python style for loop in js, type

Answer 102

myArray.forEach(function(value, index) {
console.log(value);
})

Question 103

node: To import a library, type

Answer 103

var libraryName = require(“libraryName”)

Question 104

node: To turn a json string into a json object, type

Answer 104

JSON.parse(jsonString)

Question 105

node: To turn a json object into a json string, type

Answer 105

JSON.stringify(jsonObject)

Question 106

node: you can access value one in var jsonObject = {key1: “value1”} by typing

Answer 106

jsonObject.key1

Question 107

node: To import a file in the same directory, type

Answer 107

var myFile = require(“./myFile”)

nore: the ./ path is mandatory

Question 108

node: To expose a function to people importing your file, type

Answer 108

module.exports.exposedFunctionName = localFunctionName;

Question 109

node: To access any arguments you pass into the command line when running a script e.g. node script.js param1 param2, type

Answer 109

process.argv.slice(2)

Question 110

node: To go to a local host port, type the url

Answer 110

http://localhost:1337/

Question 111

node: To create a server, type

Answer 111

var http = require(‘http’);

var server = http.createServer(function (req, res) {
res.writeHead(200);
res.end(‘Hello, World!\n’);
});

server.listen(1337);

Question 112

node: After the function res.end() is executes inside the response

Answer 112

the browser stops listening for a response

Question 113

The local IP address for all computers is

Answer 113

127.0.0.1

Question 114

node: http.createServer(myFunction(req, res)); sends your function

Answer 114

an argument which is a request object with has and attribute called req.url, which returns everything after the root domain including get params

Question 115

javascript: To create an object using a constructor function, type

Answer 115

function ConstructorFunc(param1, param2) {
  this.attribute1 = param1;
  this.attribute2 = param2;
  this.functionName = function() { console.log("string") }
}

Question 116

javascript: To instantiate an object made by a constructor function, type

Answer 116

var myInstance = new ConstructorFunc(“param1”, “param2”)

Question 117

javascript: To turn a function call into a constructor function you must

Answer 117

precede the function name with "new"
e.g.
var myInstance = new ConstructorFunc("param1", "param2")

Question 118

javascript: By convention for constructor functions, people

Answer 118

capitalize the first letter

Question 119

javascript: To add a function to a constructor function that does not reload every time the constructor function is instantiated, use

Answer 119

ConstructorFuncName.prototype.functionName = function() {
return “string”
}

Question 120

javascript: The DOM is

Answer 120

the javascript representation of the page

Question 121

javascript: For websites that are rendering over 75KB of JSON data, time to first paint

Answer 121

is lower using server side rendering on both mobile and web

Question 122

javascript: For websites that are rendering below 75KB of JSON data, time to first paint is

Answer 122

about the same using client or server side rendering on both mobile and web

Question 123

javascript: For websites that are rendering over 75KB of JSON data, time to last paint fastest on

Answer 123

server side rendering on both mobile and web

Question 124

jquery: To return in inner html of a jquery object, type

Answer 124

$(“.css-class”).html()

Question 125

javascript: To evaluate the key name in a json object, type

Answer 125

{ [varName]: “value” }

Question 126

jquery: To scroll to bottom of div, type

Answer 126

var myDiv = $('.css-class');
var height = myDiv[0].scrollHeight;
myDiv.scrollTop(height);

Question 127

node: To update node, type

Answer 127

sudo npm cache clean -f
sudo npm install -g n
sudo n stable

Question 128

javascript: To run an anonymous function

Answer 128

surround it with parentheses

Question 129

javascript: To create a script tag, add a src and type attribute to it and append it to the head, type

Answer 129

var elementName = document.createElement(“script”);

mf. type = “text/javascript”;
mf. async = true;
mf. src = “//www.cdn.com/id.js”;
document. getElementsByTagName(“head”)[0].appendChild(elementName);

Question 130

javascript: To set the html of the body tag to a string, type

Answer 130

document.getElementsByTagName(“body”)[0].innerHTML = “script”

Question 131

javascript: How jsonp works is

Answer 131

dynamically create a script tag with javascript
make the src the api endpoint you want
set the query string to ?callback=callbackFunctionName
this request will return your json data as an argument to a function named callbackFunctionName and will run the function so define the callback function that will handle the data before you make the dynamic script request
to return the data from api

Question 132

javascipt: Jsonp is

Answer 132

a way to overcome the single origin policy which prevents browsers from making an ajax request to a URL other than the current

Question 133

javascript: To run new javascript that was added to the page, type

Answer 133

eval(scriptName)

Question 134

javascript: To check if a browser has a touch screen or not, type

Answer 134

function isMobile() {
  try{ document.createEvent("TouchEvent"); return true; }
  catch(e){ return false; }
}

Question 135

jquery: To run a script only if the width of the screen is something, type

Answer 135

$(document).ready(function() {      
  var isMobile = window.matchMedia("only screen and (max-width: 760px)");

if (isMobile.matches) {
…
}
});

Question 136

javascript: To insert a new element into the top of a div full of elements, type

Answer 136

parentElement.insertBefore(newElement, parentElement.childNodes[0])

Question 137

javascript: To add a class to an element in vanilla js, type

Answer 137

document.querySelector(“div”).className += “ other-class”;

Question 138

jquery: To traverse up to the parent div then to the next div, then it’s children, type

Answer 138

$(element).parent().next().children()

Question 139

javascript: To start an html5 video at a certain spot after it loads, type

Answer 139

document.querySelector(‘video’).addEventListener(‘loadedmetadata’, function() {
this.currentTime = 10;
}, false);