Book Image

Web Developer's Reference Guide

By : Joshua Johanan, Talha Khan, Ricardo Zea
Book Image

Web Developer's Reference Guide

By: Joshua Johanan, Talha Khan, Ricardo Zea

Overview of this book

This comprehensive reference guide takes you through each topic in web development and highlights the most popular and important elements of each area. Starting with HTML, you will learn key elements and attributes and how they relate to each other. Next, you will explore CSS pseudo-classes and pseudo-elements, followed by CSS properties and functions. This will introduce you to many powerful and new selectors. You will then move on to JavaScript. This section will not just introduce functions, but will provide you with an entire reference for the language and paradigms. You will discover more about three of the most popular frameworks today—Bootstrap, which builds on CSS, jQuery which builds on JavaScript, and AngularJS, which also builds on JavaScript. Finally, you will take a walk-through Node.js, which is a server-side framework that allows you to write programs in JavaScript.
Table of Contents (22 chapters)
Web Developer's Reference Guide
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
9
JavaScript Expressions, Operators, Statements, and Arrays
Index

Promises


In JavaScript, many actions are asynchronous. A great example of this is an AJAX request. When the request is sent, you do not know when or even if a request will be returned. This is where promises come in.

A promise is an object that will promise to run a function once an asynchronous event has happened. In our example, the event will be the request returning. This could be in a few milliseconds or longer, depending on the timeout setting.

In addition to tracking successful events, promises can be rejected. This allows the object that was waiting for the response to do something different.

Note

Visit https://promisesaplus.com/ for the complete specification for using promises in JavaScript. Promises or promise-like objects are applicable in almost any JavaScript that you may write.

$q

This is the service that implements promises:

$q.defer()

Return value

This returns a deferred object.

Description

This is the core of building and using promises. The first thing is to get a deferred object...