Getting MEAN – Designing a MEAN stack architecture

A common MEAN stack architecture

A common way to architect a MEAN stack application is to have a representational state transfer (REST) API feeding a single-page application (SPA). The API is typically built with MongoDB, Express, and Node.js, with the SPA being built in Angular. The approach is particularly popular with those who come to the MEAN stack from an Angular background and are looking for a stack that gives a fast, responsive API. Figure 2.1 illustrates the basic setup and data flow.

fig_2-1

What is a REST API?

REST stands for REpresentational State Transfer, which is an architectural style rather than a strict protocol. REST is stateless – it has no idea of any current user state or history.

API is an abbreviation for application program interface, which enables applications to take to each other.

So a REST API is a stateless interface to your application. In the case of the MEAN stack, the REST API is used to create a stateless interface to your database, enabling a way for other applications to work with the data.

Figure 2.1 is a great setup, ideal if you have or intend to build an SPA as your user-facing side.

  • Angular is designed with a focus on building SPAs, pulling in data from a REST API, as well as pushing it back.
  • MongoDB, Express, and Node.js are also extremely capable when it comes to building an API, using JSON all the way through the stack, including the database itself.

This is where many people start with the MEAN stack, looking for an answer to the question, "I've built an application in Angular; now where do I get the data?"

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Getting MEAN – Introducing full-stack development

The MEAN stack is a pure JavaScript stack comprised of four main technologies, with a cast of supporting technologies:

  • MongoDB — the database
  • Express — the web framework
  • Angular — the front-end framework
  • Node.js — the web server

Why the MEAN stack specifically?

The MEAN stack pulls together some of the "best-of-breed" modern web technologies into a very powerful and flexible stack. One of the great things about the MEAN stack is that it not only uses JavaScript in the browser, it uses JavaScript throughout. Using the MEAN stack, you can code both the front end and back end in the same language.

The principle technology allowing the this to happen is Node.js, bringing JavaScript to the back end.

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TypeScript as a language for Angular applications

The reason is that developing in JavaScript isn’t overly productive. Say a function expects a string value as an argument, but the developer mistakenly invokes it by passing a numeric value. With JavaScript, this error can be caught only at run- time. Java or C# compilers won’t even compile code that has mismatching types, but JavaScript is forgiving because it’s a dynamically typed language.

On larger projects, good IDE context-sensitive help and support for refactoring are important. Renaming all occurrences of a variable of function name in spatially typed languages is done by IDEs in a split second, even in projects that have thousands oaf lines of code; but this isn’t the case in JavaScript, which doesn’t support types. IDEs can help with refactoring much better when the types of the variables are known.

To be more productive, you may consider developing in a statically typed language and then convert the code to Javascript for deployment. Currently there are dozens of languages that compile to JavaScript. The most popular are TypeScript, CoffeeScript, and Dart.

Why not use the Dart language?

  • Interoperability with third-party Javascript libraries isn’t that great.
  • Development in Dart can be done only in a specialized version of the Chrome browser (Dartium) that comes with the Dart VM.
  • The generated JavaScript isn’t easily readable by a human.
  • The community of Dart developers is rather small.

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JavaScript definite guide – Arrays

An array is an ordered collection of values. Each value is called an element, and each element has a numeric position in the array, known as its index.

  • JavaScript arrays are untyped: an array element may be of any type, and different elements of the same array may be of different types. Array elements may even by objects o other arrays, which allows you to create complex data structures, such as arrays of objects and arrays of arrays.
  • JavaScript arrays are zero-based and use 32-bit indexes: the index of the first element is 0, and the highest possible index is 4294967294 (2^32−2 ), for a maximum as needed and there is no need to declare a fixed size for the array when you create it or to reallocate it when the size changes.
  • JavaScript arrays may be sparse: the elements need not have contiguous indexes and there may be gaps.
  • Every JavaScript array has a length property.
    • For non sparse arrays, this property specifies the number of elements in the array.
    • For sparse arrays, length is larger than the index of all elements.

JavaScript arrays are specialized form of JavaScript object, and array indexes are really little more than property names that happen to be integers. Implementations typically optimize arrays so that access to numerically indexed array elements is generally significantly faster than access to regular object properties.


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iOS development with Swift 3 – Your first iOS app

What is Swift?

Swift is the modern language created by Apple which got the Apple developer world buzzing. While loved by iOS developers, Objective-C was at the same time seen by many others as an outmoded language – a verbose and peculiar syntax, and with an unsafe type system. Built as a modern alternative to Objective-C, Swift was designed with specific enhancements in mind, specifically safety, performance, and expressiveness.

  • _Safety_ — Swift introduced several programming concepts to reduce some common programmer mistakes. These include strong typing, optionals and error handling.
  • _Performance_ — Apple has introduced internal optimizations to ensure that Swift runs fast. Xcode also provides warnings to encourage you to write code that ensures your app is running optimally.
  • _Expressiveness_ — Expressive code has the right balance between containing a clear meaning and being succinct.

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日语谓语的各种形态 – “基本形”

动词的“基本形“

语法解释

“基本形”是动词的基本形式。词典中的词条都使用这一形式。各类动词“ます形”去掉“ます”的形式和“基本形”的关系对应如下:

  • 一类动词:“基本形”最后的发音为“う”段,“ます形”去掉“ます”后的发音为“い”段。
  • 二类动词:“基本形”为“ます形”去掉“ます”后加“る”。
  • 三类动词:“基本形”分别为“来る”和“する”,“ます形”去掉“ます”后则为“来”和“し”。

fig_20-1-1

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日语谓语的各种形态 – 敬体形和简体形

语法解释

在口语里,日语的谓语形式根据说话人和听话人之间的上下关系,亲疏关系的不同而不同。对长辈或关系不太亲密的人使用的形式为敬体形。与此相反,如对方是自己的同辈或晚辈,或关系比较密切时则使用“简体形”。“简体形”是不使用“ます” ”です”的形式。

动词本身就具有“敬体形”和“简体形”,如“〜ます” “〜ません” “〜ました” “ませんでした”等四种礼貌的表达形式即是“敬体形”,而以前所学的动词的“基本形” “ない形” “た形”都属于简体形。但一类形容词、二类形容词和名词本身没有“敬体形”和“简体形”之分,只有在作谓语时,其谓语形式才具有“敬体形”和“简体形”。

动词的简体形

fig_1

  • 森さんは 毎晩 テレビを 見る。
  • コーヒー 飲む?

    ー ううん、飲まない。

  • 昨日 テレビ、 見た?

    ー ううん、 見なかった。

注意:简体会话中常常省略助词。

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Functional Programming in JavaScript — Few data structures, many operations

Few data structures, many operations

This chapter covers:

  • Understanding program control and flow
  • Reasoning efficiently about code and data
  • Unlocking the power of map, reduce and filter
  • Discovering the Lodash.js library and function chains
  • Thinking recursively

In this chapter, I’ll introduce you to a few useful and practical operations like map, reduce and filter that allow you to traverse and transform data structures in a sequential manner. These operations are so important that virtually all functional programs use them in one way or another. They also facilitate removing manual loops from your code, because most loops are just specific cases handled by these functions.

You’ll also learn to use a functional JavaScript library called Lodash.js. It lets you process and understand not only the structure of your application, but also the structure of your data. In addition, I’ll discuss the important role recursion plays in functional programming and the advantages of being able to think recursively. Building on these concepts, you’ll learn to write concise, extensible and declarative programs that clearly separate control flow from the main logic of your code.

Understanding your application’s control flow

The path a program takes to arrive at a solution is known as its control flow. An imperative program describes its flow on path in great detail by exposing all the necessary steps needed to fulfill its task. These steps usually involves lots of loops and branches, as well as variables that change with each statement. At a high level, you can depict a simple imperative program like this:

var loop = optC()
while (loop) {
  var condition = optA()
  if (condition) {
    optB1
  }
  else {
    optB2()
  }
  loop = optC()
}
optD()

Figure 3.1 shows a simple flowchart of this program.

fig_3-1

On the other hand, declarative programs, specifically functional ones, raise the level of abstraction by using a minimally structured flow made up of independent black-box operations that connect in a simple topology. These connected operations are nothing more than higher-order functions that move state from one operation to the next, as shown in figure 3.2. Working functionally with data structures such as arrays lends itself to this style of development and treats data and control flow as simple connections between high-level components.

fig_3-2

This produces code more or less like the following:

optA().optB().optC().optD() // Connecting via dots suggests the presence of a shared object that contains these methods.

Chaining operation in this manner leads to concise, fluent, expressive programs that let you separate a program’s control flow from its computational logic. Thus, you can reason about your code and your data more effectively.

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Functional Programming in JavaScript — Higher Order JavaScript

Higher Order JavaScript

This chapter covers

  • Why JavaScript is a suitable functional language
  • JavaScript as a language that enables multi paradigm development
  • Immutability and policies for change
  • Understanding higher-order and first-class functions
  • Exploring the concepts of closures and scopes
  • Practical sue of closures

As applications get bigger, so does their complexity. No matter how good you think you are, turmoil is unavoidable if you don’t have the proper programming model in place.In chapter 1, I explained the reasons functional progrmaming is a compelling paradigm to adopt. But paradigms by themselves are just programming modes that need the right host language to come to life.

In this chapter, I take you on a fast-pass tour of a hybrid langue that mixes both object-oriented as well as functional programming: JavaScript. Of course, this is by no means an extensive study of the language; rather, I’ll focus on what allows JavaScript to be used functionally as well as where it falls short. One example of this is the lack of support for immutability. In addition, this chapter covers higher-order functions and closures, which totogethaer from the backbone that allows yo to write JavaScript in a function style. Without further ado, let’s dive in.

Why JavaScript?

I began by answering the question, ” Why functional?” Another question that comes to mind is, “Why JavaScript?” The answer to this question is simple: omnipresence. JavaScript is a dynamically typed, object-oriented, general-purpose language with an immensely expressive syntax. It’s one of the most ubiquitous languages ever created and can be seen in the development of mobile applications, se sites, web severs, desktop and embedded applications, and even databases. Given its extraordinary adoption as the language of the web, it begs to reasons the JavaScript is by far the most widely used FP language ever created.

Despite its C-like syntax, JavaScript draws lots of inspiration from functional languages like Lisp and Scheme. The commonalities lie in their support for higher-older functions, closures, array literals, and other features that make JavaScript a superb platform for applying FP techniques. In fact, functions re the main units of work in JavaScript, which means they’re used not only to drive the behavior off our applications, but also to define objects, create modules, and handle events.

JavaScript is actively evolving and improving. Backed by the ECMAScript (ES) standard, its next major release, ES6, adds many more features to the language: arrow functions, constants, iterators, promise, and other features that suit functional programming very well.

Despite the fact that it has lots of powerful functional features, it’s important to know that javaScript is as objet-oriented as it is functional. Unfortunately, the latter is rarely seen; most developers use mutable operations, imperative control structures, and instance state changes on objects, which are all virtually eliminated when adopting a functional style. Nevertheless, I feel it’s important to spend some time talking about JavaScript as an object-oriented language first so that you can better appreciate the key differences between the two paradigms. This will allow you to leap into functional programming more easily.

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