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DART Essentials
DART Essentials

DART Essentials: Design and build full-featured web and CLI apps using the powerful Dart language and its libraries and tools

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DART Essentials

Chapter 2. Practical Dart

This chapter will focus on the most common features of Dart that you'll use every day for your next Dart project. In this chapter, we'll look at:

  • Manipulating DOM and HTML elements
  • Future-Based API, Dart's built-in library for working with asynchronous calls
  • Creating Ajax requests in Dart
  • How packages work in Dart
  • Calling JavaScript from Dart
  • Calling Dart from JavaScript

The whole chapter is intended to be very practical. We'll create a small app that reads a JSON dictionary and lets you search among all the terms in it. To make it more complicated, we'll implement a so-called fuzzy search algorithm, which doesn't search exact matches but the same order of characters instead.

Optimizing DOM tree manipulations

We've already seen some basic manipulation with HTML elements in Chapter 1, Getting Started with Dart, and we'll make a few notes about it here.

The Dart library wraps standard JavaScript element classes and methods with more unified names. Classes that represent HTML elements don't start with the HTML prefix, so for example, HTMLDivElement is called DivElement in Dart. Take a look at this JavaScript snippet:

elm.addEventListener('client', function() { /* ... */ });

Instead of binding event listeners with the preceding code, Dart uses the so-called Stream API, where you don't bind listeners directly to the element you subscribe but to a Stream object instead, which emits all events. Each HTML element has all the default event emitters, such as onClick or onKeyPress:

elm.onClick.listen((e) { /* ... */ });

The listen()method returns a StreamSubscription object that can be used to unsubscribe the listener.

Streams have many methods...

The documentation search app

We're going to write an app that can search among many terms and show some simple detail for each of them. The search input field will have an autocomplete feature with a list of all the terms that match our search string.

Particularly, we'll use the documentation for PHP with 9,047 functions and write a fuzzy search algorithm that will search in it.

Fuzzy search is used in IDEs such as PHPStorm or PyCharm and also in the popular text editor Sublime Text. It doesn't search just for the strings that start with your search term but it checks whether the order of characters in your term and in the checked string is the same. For example, if you type docfrg, it will find DocumentFragment because the letters in DocumentFragment are in the same order as docfrg.

This is very handy because when there are a lot of functions with the same prefix, you can start typing with just the first character and then jump to the middle of the word and it's very likely...

Combining Dart and JavaScript

Using Dart in JavaScript and JavaScript in Dart is very easy, although there are some limitations right now that will hopefully be resolved in the future. Basically, when exchanging data between JavaScript and Dart, all you have to do is to wrap/unwrap Dart objects with JsArray, JsFunction, or JsObject proxy classes from the dart:js built-in package.

Some built-in types don't need any proxy wrapper. The most common are null, bool, num, String, DateTime, HtmlCollection, Event, Node, and NodeList.

Note

Maybe you've already seen somebody using a package:js/js.dart package. This is the old Dart-JS interoperation package, which is deprecated in favor of dart:js.

Using Dart in JavaScript

Let's say we're writing a JavaScript app where we want to reuse our existing FuzzySearch class and print all results to the console.

As of now, we can't just expose the class definition and then create instances of it in JavaScript. We can't even create an...

Dart MythBusters

There are some prejudgments about Dart, usually from frontend developers who have never used it or for some reason decided that they don't want to use it at any cost:

  • It's just another abstraction layer like CoffeeScript or TypeScript and will become redundant with ECMAScript 6: Dart is more than this. It's a full-stack, modern, object-oriented, class-based language with its own standalone VM, IDE, debugger, profiler, and everything (see Chapter 1, Getting Started with Dart). It takes the best from many of today's languages. You can watch the keynote from Dart Summit 2015 about future plans with Dart (https://www.youtube.com/watch?v=FiXiI2Atexc).
  • It looks like C or Java; it's unnecessarily complicated to do anything with it: More or less, your code is going to be the same length as vanilla JavaScript plus jQuery. You can see a list of synonyms of Dart and other languages at https://www.dartlang.org/docs/synonyms/.
  • It's not natively supported anywhere...

Summary

This chapter focused on a very practical aspect of Dart. From Streams and the Future-Based API to Ajax, Dart 1.9 took a significant step forward in simplifying the usage of asynchronous APIs using new async and await keywords. If you don't find yourself familiar with the Future-Based API, at least try to understand the new async and await features and try to compare Dart's approach to an asynchronous code to what you already know from JavaScript.

We also saw that Dart can work with existing JavaScript code and vice versa. There are some limitations, but the Dart development team announced that they'll focus on simplifying the integration of Dart and JavaScript so the future looks promising.

In the next chapter, we'll focus more on HTML5-specific APIs.

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Description

This book is targeted at expert programmers in JavaScript who want to learn Dart quickly. Some previous experience with OOP programming in other languages and a good knowledge of JavaScript are assumed.

Who is this book for?

This book is targeted at expert programmers in JavaScript who want to learn Dart quickly. Some previous experience with OOP programming in other languages and a good knowledge of JavaScript are assumed.

What you will learn

  • Learn about the Dart language syntax, libraries, and package manager
  • Use existing JavaScript libraries in Dart and call Dart code from JavaScript
  • Handle asynchronous calls with FutureBased API and use HTML5 features in Dart
  • Write example apps with Web Components and polymer.dart
  • Develop web apps using AngularDart
  • Test apps with unit tests and analyze them with Observatory
  • Explore CLI apps, WebSocket servers, and serverside scripting in Dart
  • Extend the Standalone Dart VM with C/C++ native extensions
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Publication date, Length, Edition, Language, ISBN-13
Publication date : May 25, 2015
Length: 232 pages
Edition : 1st
Language : English
ISBN-13 : 9781783989607
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Product Details

Publication date : May 25, 2015
Length: 232 pages
Edition : 1st
Language : English
ISBN-13 : 9781783989607
Vendor :
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Table of Contents

10 Chapters
1. Getting Started with Dart Chevron down icon Chevron up icon
2. Practical Dart Chevron down icon Chevron up icon
3. The Power of HTML5 with Dart Chevron down icon Chevron up icon
4. Developing a Mobile App with Dart Chevron down icon Chevron up icon
5. Web Components and polymer.dart Chevron down icon Chevron up icon
6. AngularDart Chevron down icon Chevron up icon
7. Server-side Applications with Dart Chevron down icon Chevron up icon
8. Testing and Profiling the Dart Code Chevron down icon Chevron up icon
9. Writing Native Extensions for the Standalone Dart VM Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.8
(4 Ratings)
5 star 75%
4 star 25%
3 star 0%
2 star 0%
1 star 0%
R. Jankie Jun 09, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I got invited to review this book and it was my pleasure to do so. The writer took the effort to explain Dart and some fundamental artefacts in a compact and clear way. Reviewing this book was a nice experience. To the point as if the writer knew what you were thinking :)
Amazon Verified review Amazon
S. L. Aug 29, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Excellent overview of the Dart language, and how it is used on the web and the server.
Amazon Verified review Amazon
Ivan Zaitsev Jun 15, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Advanced introduction to Dart. From "Getting started" and common tasks to mobile applications, standalone applications, AngularDart and native extensions. Author accents occasions when Dart is especially suitable solution.
Amazon Verified review Amazon
Amazon Customer Jun 12, 2015
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
I was surprised and overjoyed to learn that another book on Dart had been completed and published, and this one did not disappoint. Written clearly and concisely, the book makes an excellent case for Dart as an alternative to JavaScript for programming serious web and server applications.If I have any gripes at all, they'd be that a few of the chapters (notably those on AngularDart and Polymer.dart) are a bit out of date, but that's not the fault of the author, as those technologies move very fast and are in a transitional period just now. The core concepts related here are timeless, though, and fortunately, the author did get a few notes in before publication about the current state of those frameworks and the impending deprecation of the Dart Editor.The chapters on mobile development and writing native extensions for the Dart virtual machine help the book stand out, as those topics don't get enough attention from other sources.Overall, Dart Essentials is a welcome addition to the growing library of books on Dart, and better written than many.
Amazon Verified review Amazon
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