Megan Taylor

front-end dev, volunteacher, news & data junkie, bibliophile, Flyers fan, sci-fi geek and kitteh servant

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Thinkful Unit 3 Comprehension Checks

Lesson 1

Assignment 1

Describe what event binding is and how it can be used to make your pages interactive.

Event binding attaches a handler to an event for the DOM elements.

Events can be:

  • A mouse click
  • A web page loading
  • Taking mouse over an element
  • Submitting an HTML form
  • A keystroke on your keyboard

So you can have elements appear, disappear, animate, etc., based on events.

What are the advantages of using the first block of code over the second?

$(‘#my-div’).on(‘click’, function() { ...do stuff...; });
vs.
$(‘#my-div’).click( function() { ...do stuff...; });

the ability to bind to multiple events at once
use “namespaced” events

What does .preventDefault() do, and when would you use it?

prevents the default action of an event, like clicking on a link or a button

What does .stopPropagation() do, and when would you use it?

prevents ‘event bubbling’ – when an event is triggered for a nested element and then is triggered for every element up the DOM.

How and why would you use this in an event handler?

this allows you to target a specific element, while still binding to a high-level element. This is called event delegation.

Give an example of event delegation and explain its advantages.

Event delegation lets you bind fewer event handlers, which can be a big performance gain. It also lets you bind to parent elements and know that event handlers will fire as expected even if the contents of that parent element change.

Assignment 2

How can you set the fast and slow speeds for jQuery animations?

The predefined speeds are specified in the jQuery.fx.speeds object; you can modify this object to override the defaults, or extend it with new names:

// re-set an existing predefined speed
jQuery.fx.speeds.fast = 50;
// Since we've re-set the 'fast' speed, this will now animate over the
// course of 50 milliseconds
$( '.hidden' ).hide( 'fast' );

Why might you be further ahead using CSS animations instead of jQuery for mobile devices?

In modern browsers, and especially on mobile devices, it is often much more efficient to achieve animations using CSS rather than JavaScript.

What must you do to the spelling of properties like font-size that have hyphens if you want to reference them in a jQuery animation method?

If you want to animate a CSS property whose name includes a hyphen, you will need to use a “camel case” version of the property name if you do not quote the property name. For example, the font-size property must be referred to as fontSize.

How can you stop a jQuery effect?

.stop() will stop currently running animations on the selected elements.
.delay() will pause before the execution of the next animation method. Pass it the number of milliseconds you want to wait.

Lesson 2

Assignment 1

Memorize both syntactically correct ways you can call jQuery’s .ajax() method.

$.ajax({
 url: '/data/people.json',
 dataType: 'json',
 success: function( resp ) {
 $( '#target').html( resp.people[0].name );
 },
 error: function( req, status, err ) {
 console.log( 'something went wrong', status, err );
 }
});
$.ajax( '/data/people.json', {
  type: 'GET',
  dataType: 'json',
  success: function( resp ) {
    console.log( resp.people );
  },
  error: function( req, status, err ) {
    console.log( 'something went wrong', status, err );
  }
});

What are success and error callbacks, and how do they work with .ajax()?

Success Callback: A function to be called if the request succeeds.
Error Callback: A function to be called if the request fails.

Make sure you understand that how and why the return command of an ajax() call will return before the server to which the request was made has responded.

AJAX requests run asynchronously —  the $.ajax method returns before the request is finished, and this function’s return statement runs before the request is complete.

What is JSON and what can you use it to represent?

JSON is a string representation of data.

What are the .get() and .post() methods?

If we’re just making a simple request — and if we don’t care about error handling — jQuery provides several “convenience methods” that let us use an abbreviated syntax. Each of these methods takes a URL, an optional data object, and an optional callback for handling a successful request.

$.get( '/data/people.html', function( html ){
  $( '#target' ).html( html );
});
$.post( '/data/save', { name: 'Rebecca' }, function( resp ) {
  console.log( JSON.parse( resp ) );
});

We can send data with our request by passing an object as the second argument to one of the convenience methods.
For a GET request, this data will be appended to the URL as a query string; for a POST request, it will be sent as form data.

How can you use jQuery to serialize and submit form data?

The .serialize() method converts form input to a query string format.

.ajax() calls return a jqXHR object. What are the .then(), .done(), .fail(), and .always() methods on jqXHR objects for?

.then() – attach success and error callbacks
.done() – attach success callback
.fail()– attach error callback
.always() –  attach callback that runs on success or failure

What is JSONP and what does it allow you to do?

Allows you to use data even though it is hosted on another server.

What does an ajax call with JSONP look like in jQuery?

$.ajax({
 url: '/data/search.jsonp',
 data: { q: 'a' },
 dataType: 'jsonp',
 success: function( resp ) {
 $( '#target' ).html( 'Results: ' + resp.results.length );
 }
});

What is the .getJSON() method?

A convenience method to make a JSONP request; if the URL includes callback=? or similar, then jQuery will treat it as a JSONP request.

$.getJSON( '/data/search.jsonp?q=a&callback=?',
 function( resp ) {
 $( '#target' ).html( 'Results: ' + resp.results.length );
 }
);

How can you use $.Deferred() to return a promise?

The deferred.promise() method allows an asynchronous function to prevent other code from interfering with the progress or status of its internal request.

Lesson 3

Assignment 1

What is JSON?

JSON (or JavaScript Object Notation) is a lightweight, easy and popular way to exchange data.

What’s a callback and how does it work in the context of a jQuery .getJSON() request?

A callback is a function that is passed to another function to run.

What is JSONP and what does it allow you to do?

JSONP (or JSON with padding) allows a script to fetch data from another server on a different domain.

Assignment 2

What is encapsulation and why is it important?

Encapsulation in an important organization concept for code. It separates code into distinct pieces.
Broadly, encapsulation does one or both of these:

  • restricts access to some of the object’s components
  • facilitates the bundling of data with the methods (or other functions) operating on that data

How can you use object literals to namespace functions?

An object literal is perhaps the simplest way to encapsulate related code. It doesn’t offer any privacy for properties or methods, but it’s useful for eliminating anonymous functions from your code, centralizing configuration options, and easing the path to reuse and refactoring.


// An object literal
var myFeature = {

    myProperty: "hello",

    myMethod: function() {
        console.log( myFeature.myProperty );
    },

    init: function( settings ) {
        myFeature.settings = settings;
    },

    readSettings: function() {
        console.log( myFeature.settings );
    }

};

myFeature.myProperty === "hello"; // true

myFeature.myMethod(); // "hello"

myFeature.init({
    foo: "bar"
});

myFeature.readSettings(); // { foo: "bar" }

The object literal above is simply an object assigned to a variable. The object has one property and several methods. All of the properties and methods are public, so any part of your application can see the properties and call methods on the object. While there is an init method, there’s nothing requiring that it be called before the object is functional.

Explain the DRY concept.

Don’t repeat yourself; if you’re repeating yourself, you’re doing it wrong.