Introduction to node.js
- 2. Agenda What is node.js? Why node.js? How node.js works? How node.js is different from others? What can be done with node.js? Few examples Who is using node.js?
- 3. Why Node.js
- 5. what is node.js? “Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine. Node.js uses an event-driven, Asynchronous non-blocking I/O model that makes it lightweight and efficient. What is v8 engine? ● It is a open source javascript engine. Developed by Chromium. ● It is written in c++ ● V8 compiles JavaScript to native machine code, thereby compiling and executing JavaScript code at a lightning speed
- 6. Difference between synchronous and asynchronous ● It waits for each operation to complete, after that it will execute next operation. ● Step-By-Step Execution ● It will never waits for each operation to complete, rather it executes all the operations at a time. The results of each operation will be handled once result is available. ● CallBacks are used to handle results
- 7. Synchronous example Example: var result = database.query("SELECT * FROM hugetable"); console.log(“db operation is done”); console.log("Hello World"); Output: db operation is done Hello World
- 8. Asynchronous Example Example: database.query("SELECT * FROM hugetable", function(rows) { var result = rows; console.log(“After db operation”); }); console.log("Hello World"); Output: Hello world After db operation
- 9. Asynchronous Example Example: database.query("SELECT * FROM hugetable", function(rows) { var result = rows; console.log(“After db operation”); }); console.log("Hello World"); Output: Hello world After db operation
- 11. Few more examples... setTimeout(sayHello,1000); Function sayHello(){ console.log(“Hello WiCheck Team”); } console.log(“VANAKKAM”); Output: VANAKKAM Hello WiCheck Team
- 12. How to create callbacks? function SayHello(str, callback){ //do what ever with str // finally call callback callback(); } sayHello(“Alethea” , function(){ console.log(“I’M CallBack”); });
- 13. Phantomjs ● Headless browser. var page = require('webpage').create(); page.open('http://www.google.com', function(status) { console.log("Status: " + status); if(status === "success") { page.render(‘google.png'); } phantom.exit(); });
- 15. There is a problem with callbacks.... getData(function(a){ getMoreData(a, function(b){ getMoreData(b, function(c){ getMoreData(c, function(d){ getMoreData(d, function(e){ ... }); }); }); }); });
- 16. How to avoid callbacks? ● Promises ● Generators ● Async/wait ● Third party libs(async.js)
- 17. Advantages of Node.js ● JavaScript In the backend and frontend ● Best for web servers(http) ● Node.js is a boon for building highly scalable Web App ● Node.js excels at Real-time applications(Stock,chat,video) ● Data streaming gets easier.