Who knew JavaScript would end up being a compelling language for wrting serer-side applications?
- "Toy" language in 90's
- Ajax revolution in 2005
- GMail
- Google Map
- jQuery released in 2006
- Google Chrome release in 2008
- JavaScript performance has improved at an incredibly fast rate
- Heavy competition between browser vendors
- Node.js debuted in 2009
- Changed the types of applications you can build on the web
Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient. Node.js' package ecosystem, npm, is the largest ecosystem of open source libraries in the world.
- JavaScript environment for server-side(back-end) development
- Brings JavaScript to the server in much the same way a browser brings JavaScript the client.
- Allows you to build scalable network applications using JavaScript
- Very fast because it's mostly C code
- Uses V8 Engine, the virtual machine that powers Google Chrome
- Uses an event-driven, non-blocking I/O model
- Node.js = Runtime Environment + JavaScript Library
- Website
- English : https://nodejs.org/en/
- Korean : https://nodejs.org/ko/
-
A Web Framework
- Node.js is a platform for JavaScript applications, and it's not to be confused with a framework.
- It's a common misconception to think of Node.js as Rails or Django for JavaScript, whereas it's much lower level.
- We'll talk about a popular frameowork for Node.js called Express.js later.
-
Multi-threaded
- You can think of it as a single threaded server.
- But it can handle concurrent operations without multiple threads of execution, so it can scale pretty well.
- Used to run only on browsers
- Cross Platform(O/S)
- Limitation
Node.js packages are growing faster than Ruby, Pathon and even Java!
Ahead of its annual conference in September 2016, Github shared its report here.
- Develepers can write web applications in one language
- Reduce the context switch between client and server development
- JavaScript is unavoidable if you've done any programming for the web
- Full-stack development trend and Start-up booms
- Most coding schools/bootcamps teach JavaScript as the first language
- Node.js is a part of the MEAN stack.
- JSON is a very popular data interchange format today and is native to JavaScript
- JavaScript is the language used in various No SQL (MongoDB, CouchDB)
MEAN is an opinionated fullstack javascript framework which simplifies and accelerates web application development.
- MongoDB is the leading NoSQL database, empowering businesses to be more agile and scalable.
- Express is a minimal and flexible node.js web application framework, providing a robust set of features for building single and multi-page, and hybrid web applications.
- AngularJS lets you extend HTML vocabulary for your application. The resulting environment is extraordinarily expressive, readable, and quick to develop.
- Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications
Node.js is ideal for I/O bound applications, but not so great for CPU-heavy applications.
- Data Intensive Real-time Applications (DIRT)
- Single Page Applications
- JSON APIs (RESTful Web Services)
- Data Streaming Applications (Music, Video)
- Websocket Server (like a chat server)
Download one-click installers for Mac or Windows here
If you know how to use HomeBrew...
$ brew install node
$ brew install npm
Make sure it's installed properly on the terminal
$ node -v
v7.0.0
$ npm -v
3.10.8
Node.js provides CLI(Command Line Interface). Using this shell program, we can execute pretty much any Node.js/JavaScript code on the terminal.
$ node
> 1 + 2
3
> 17 + 31 / 2 * 5
94.5
> 'Hello, ' + 'Node.js!'
'Hello, Node.js!'
> console.log('Hello, World!')
'Hello, World!'
> a = 1; b = 2; a + b
3
> function sqrt(n) { return n * n; }
undefined
> sqrt(3)
9
> new Date();
2017-01-03T03:43:16.185Z
> window.alert('abc');
ReferenceError: window is not definedBe careful! Unlike in a browser, the window and document global object is absent in Node.js. (Obviously we don't deal with a browser window server-side)
To start a Node.js script from a file, simply run node <filename>.
- Write hello.js.
console.log('Hello, World!');- Just run it!
$ node hello.js
Hello, World!You don't need to compile JavaScript code, because it's loaded into memory and interpreted immediately. Therefore, a lightweight text editor is highly recommended. However, if you are already familiar and comfortable with the IDE of your choice, feel free to stick with it.
Don't worry! Most of the Node.js syntax is similar to front-end JavaScript.
Automatic typecasting works well most of the time. It's a great feature that saves a lot of time and mental energy! There are only a few types of primitives.
- String
- Number (both integer and real)
- Boolean
- RegExp
- Undefined
- Null
Everything else is an object.
> 'a' === new String('a')
false
> 'a' === new String('a').toString()
true
> 'a' == new String('a')
trueBy the way, == performs automatic typecasting whereas === does not.
> typeof('a')
'string'
> typeof(new String('a'))
'object'String are just objects and nothing special about it.
> var text = 'Learn Teach Code Seoul'
undefined
> text.length
22
> text.substr(10)
'h Code Seoul'
> text.substr(10, 5)
'h Cod'
> text.split(' ')
[ 'Learn', 'Teach', 'Code', 'Seoul' ]Object notation is super readable and compact.
var car = {
color: 'white',
type: 'sedan',
owner: {
...
}
}Functions are objects in Node.js and we treat them as variables.
// Named Function
function hello(name) {
console.log('Hello,', name, '!');
return true;
}
// Anonymous Function
var hello = function(name) {
console.log('Hello,', name, '!');
return true;
};
// ES6 Arrow Function (a.k.a. lambda)
var hello = (name) => {
console.log('Hello,', name, '!');
return true;
};JavaScript treats functions like any other objects, so we can pass them to other functions as parameters. (usually, callbcks in Node.js)
var convertNum = function(num) {
return num + 10;
};
var processNum = function(num, fn) {
return fn(num);
};
processNum(5, convertNum); // 15Arrays are also objects that have some special methods to manage elements in it.
var emptyArr = [];
var numberArr = [1, 2, 3, 4, 5];
var stringArr = ['A', 'B', 'C'];
var arr = [1, 'A', {name: 'Dale'}, function() { console.log('boo'); }];Example
var fruits = ['Apple', 'Banana', 'Coconut'];
console.log(fruits.length);
var fruit1 = fruits[0];
var fruit2 = fruits[1];
var fruit3 = fruits[2];
var fruit3 = fruits[3]; // undefined
fruits[1] = "Lemon" // ["Apple", "Lemon", "Coconut"]
fruits.push("Orange"); // ["Apple", "Banana", "Coconut", "Orange"]
fruits.push("Strawberry"); // ["Apple", "Banana", "Coconut", "Orange", "Strawberry"]
delete fruits[3]; // ["Apple", "Lemon", "Coconut", , "Strawberry"]Conditional statements are used to alter the control flow of a program, based on a specified boolean condition. A conditional statement looks like this.
if (n > 1) {
console.log('the variable n is greater than 1.');
} else {
console.log('the variable n is less than or equal to 1.');
}Inside parentheses you must enter a logic statement, meaning that the result of the statement is either true or false. The else block is optional and contains the code that will be executed if the statement is false.
For loops allow you to repeatedly run a block of code a certain number of times. This for loop logs to the console ten times:
for (var i = 0; i < 10; i++) {
console.log(i);
}The first part, var i = 0, is run once at the beginning of the loop.
The variable i is used to track how many times the loop has run.
The second part, i < 10, is checked at the beginning of every loop iteration before running the code inside the loop. If the statement is true, the code inside the loop is executed.
If it is false, then the loop is complete.
The statement i < 10 indicates that the loop will continue as long as i is less than 10.
The final part, i++, is executed at the end of every loop.
This increases the variable i by 1 after each loop.
Once i reaches 10, the loop will exit.
For the complete list of methods and examples, visit the following sites.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects
Node.js is
- Built on JavaScript
- Evented and asynchronous
- Desigend for data-intensive real-time applications
- JavaScript is growing rapidly and one of the most popular programming languages 😁