Node.js quick intro
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Node.js is an event-driven platform for building scalable network applications. It uses non-blocking I/O and asynchronous calls to handle many connections concurrently without blocking. At the core of Node.js is a single-threaded event loop that processes tasks in the order they are placed into the queue, executing callbacks asynchronously without blocking the main thread. The event loop handles all incoming requests and passes them to the JavaScript engine to execute callbacks and return responses. Node.js uses the V8 JavaScript engine and runs built-in modules and third-party modules for common tasks like HTTP servers and file system access.
![Event loop illustration
// event loop
while (true) {
lock (queue) {
var tickEvents = copy(queue);
queue.empty();
}
for (var i = 0; i < tickEvents.length; i++) {
InvokeJSFunction(tickEvents[i]);
}
}
// thread-safe event pushing
lock (queue) {
queue.push(event);
}
// io call
fs.readFile(“pwd”, function(e, d){
console.log(“file data:”, d);
});](https://image.slidesharecdn.com/node-140331045943-phpapp02/85/Node-js-quick-intro-5-320.jpg)
Node.js quick intro
- 2. Node.js Platform for scalable network applications servers and clients Uses event driven, non-blocking I/O epoll, kqueue, /dev/poll, or select process never blocks, no deadlocks internal event loop
- 3. Event driven platform Non-blocking - not waiting for things to finish Uses asynchronous platform-specific API’s “Single-threaded” - sequential task execution Runs synchronous API’s in threads
- 4. Node.js architecture Based on V8 JavaScript Virtual Machine (engine) + standard library Google Chrome uses V8 too
- 5. Event loop illustration // event loop while (true) { lock (queue) { var tickEvents = copy(queue); queue.empty(); } for (var i = 0; i < tickEvents.length; i++) { InvokeJSFunction(tickEvents[i]); } } // thread-safe event pushing lock (queue) { queue.push(event); } // io call fs.readFile(“pwd”, function(e, d){ console.log(“file data:”, d); });
- 6. Callbacks var fs = require(“fs”); var cb = function(err, data){ if (err) throw err; console.log(“File contents: ” + data); } fs.readFile(“pwd1”, cb); fs.readFile(“pwd2”, cb);
- 7. Http server app var http = require('http'); http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello Worldn'); }).listen(1337, "127.0.0.1");
- 8. Node.js launching $ echo ‘console.log(“hey there”)’ | node $ node app.js
- 10. That was quick Node.js introduction Thanks