A Beginner Splurge in Node.js

Node.js: Efficient JavaScript running environment for non-blocking I/O

This article will briefly introduce the core features of Node.js and demonstrate its key functions through the command line. Node.js is based on Chrome's V8 JavaScript engine, and its non-blocking I/O and asynchronous operation mechanisms make it excellent in handling concurrent requests.

The advantages of Node.js:

• Non-blocking I/O: Node.js is designed to avoid blocking program execution by I/O operations. In traditional synchronous programming, I/O operations (such as file reading, network request) will pause program execution until the operation is completed. Node.js continues to perform other tasks while the I/O operations are in progress, significantly improving efficiency.

• Async operations: Node.js widely uses callback functions to handle asynchronous operations. The callback function is executed after the I/O operation is completed, avoiding blockage caused by synchronous operations.

• V8 JavaScript Engine: Node.js runs on the efficient V8 JavaScript engine, ensuring its performance.

Callbacks:

The callback function is the basis of Node.js asynchronous programming. They are passed as parameters to the function and are executed after the asynchronous operation is completed. Here is a simple example:

> function add(a, b, callback) { var result = a + b; callback(result); }

This add function accepts two numbers and a callback function as parameters. It calculates the sum of two numbers, then calls the callback function and passes the result to it.

> add(2, 3, function (c) { console.log('2 + 3 = ' + c) });
> add(1, 1, function (c) { console.log('Is 1 + 1 = 3? ' + (c === 3)); });

Asynchronous operation example:

Use the setTimeout function to simulate asynchronous operations:

> function doSomething(asyncCallback) { setTimeout(asyncCallback, Math.random() * 1000 + 1000); }
> doSomething(function () { console.log('This runs asynchronously.'); });
> console.log('test');

This code demonstrates the nondeterministic execution order of asynchronous callbacks.

File I/O:

Node.js provides the fs module for asynchronous file operations:

> var fs = require('fs');
> fs.writeFile('message.txt', 'Hello Node.js', function () { console.log('Saved.'); });
> console.log('Writing file...');

> fs.readFile('message.txt', {encoding: 'utf-8'}, function(err, data) { console.log(data); });

Create a web server:

Node.js' http module can be used to create a simple web server:

> var http = require('http');
> var server = http.createServer(function (request, response) { response.end('Hello Node.js'); });
> server.listen(8080);

Access localhost:8080 to see the results returned by the server.

Async/Await:

ES2017 introduces the async/await syntax, which simplifies the writing of asynchronous code:

async function sum(a,b) {
    return a + b;
}

The

await keyword can only be used in the async function and is used to wait for the resolution of the Promise.

Summary:

Node.js is an ideal choice for building high-performance network applications with its lightweight, non-blocking I/O and powerful asynchronous programming capabilities. Its JavaScript-based features also lower the development threshold.

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