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* fix: replace sh with shell fix replace terminal with shell fix replace node with js fix replace output with shell fix replace cs with csharp fix replace c++ with cpp fix replace c# with csharp fix replace javasctipt with js fix replace syntax with js fix replace unix with shell fix replace linux with shell fix replace java 8 with java fix replace swift4 with swift fix replace react.js with jsx fix replace javascriot with js fix replace javacsript with js fix replace c++ - with cpp fix: corrected various typos fix: replace Algorithm with nothing fix: replace xaml with xml fix: replace solidity with nothing fix: replace c++ with cpp fix: replace txt with shell fix: replace code with json and css fix: replace console with shell
68 lines
3.0 KiB
Markdown
68 lines
3.0 KiB
Markdown
---
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title: Node.js
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---
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<img src="https://nodejs.org/static/images/logos/nodejs-new-pantone-black.png" height="123" width="201">
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## Node.js
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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.
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#### Let's break it down.
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- JavaScript runtime built on Google Chrome's V8 JavaScript engine.
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Every browser has a JavaSript engine built in it to process JavaScript files contained in websites. Chrome uses V8, which is built using C++. Node.js also uses this super-fast engine to interpret JavaScript files.
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- Node.js uses an event-driven model.
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This means that Node.js waits for certain events to take place. It then acts on those events. Events can be anything from a click to a HTTP request. We can also declare our own custom events and make node.js listen for those events.
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- Node.js uses a non-blocking I/O model.
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We know that I/O tasks take much longer than processing tasks. Node.js uses callback functions to handle such requests.
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Let us assume that a particular I/O task takes 5 secs to execute.
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And we want to perform this I/O twice in our code.
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**Python**
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```python
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import time
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def my_io_task():
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time.sleep(5)
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print("done")
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my_io_task()
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my_io_task()
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```
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**Node.js**
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```js
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function my_io_task() {
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setTimeout(function() {
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console.log('done');
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}, 5000);
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}
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my_io_task();
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my_io_task();
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```
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Both look similar but the time taken to execute are different. The python code takes 10 seconds to execute while the Node.js code takes only 5 seconds to execute.
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Node.js takes less time because of its non-blocking I/O model. The first call to ```my_io_task()``` starts the timer and leaves it there. It does not wait for the response from the function, instead, it moves on to call the second ```my_io_task()```, starts the timer and leaves it there.
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When the timer completes it's execution taking 5 seconds, it calls the function and prints ```done``` on the console. Since, both the timers are started together, they complete together and therefore take same amount of time.
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#### NPM
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NPM is the default package manager for JavaScript runtime environment NodeJS.
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For more visit : [NPM official site](https://www.npmjs.com/)
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#### Why use NodeJS:
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1. Great for beginners. JavaScript is a beginner friendly language.
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2. Great supportive community and massive amount of modules (Express, Grunt, etc).
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3. Wide range of hosting options.
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4. Existing Front-End developers get to transfer existing JavaScript knowledge for an easier transition into Server-Side development
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#### More information:
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- [Official NodeJS site](https://nodejs.org)
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- [Node Version Manager](https://github.com/creationix/nvm/blob/master/README.md)
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- [n: Interactive NodeJS Version Manager](https://github.com/tj/n)
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- [The definitive Node.js handbook](https://medium.freecodecamp.org/the-definitive-node-js-handbook-6912378afc6e)
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