What are the characteristics of nodejs syntax?

Node.js is a JavaScript running environment built on the Chrome V8 engine. It runs JavaScript code on the server side and provides many modules and APIs, making it a very powerful server-side programming tool. The syntax of Node.js also has some characteristics. This article will introduce the following aspects in detail.

1. Callback function

The most common feature in Node.js is the use of callback function. The callback function is actually a function passed in as a parameter of another function. When the called function is completed, the callback function is called to notify the execution result. This asynchronous programming method can improve the performance and efficiency of the program, because when the program performs asynchronous tasks (I/O operations, etc.), other code can be executed at the same time without having to wait for the asynchronous tasks to complete.

For example, the following code:

fs.readFile('myfile.txt', 'utf8', function(err, data) {
  if (err) throw err;
  console.log(data);
});

fs.readFile is an asynchronous file reading function. After reading the file, the result is passed through the callback function return. The callback function is usually an anonymous function because it will only be triggered once after the asynchronous operation completes.

2. Modular programming

Node.js uses modular programming to manage code. Each file can be regarded as a module, and modules are connected through require functions to reference other modules. This approach can make the program structure clearer and easier to maintain, and can also avoid the pollution of global variables.

Such as the following code:

//  math.js
exports.add = function(a, b) {
  return a + b;
};

//  main.js
const math = require('./math');
console.log(math.add(1, 2)); // 3

math.js is a module that exposes an add## through the exports object #method. main.js introduces math.js through the require function and calls the methods in it.

3. Single-threaded, event loop

Node.js is single-threaded, which means that it uses one main thread to handle all requests and events. However, under the hood, Node.js has an event loop mechanism that handles asynchronous tasks and notifies the main thread when the task is completed.

The event loop mechanism includes the following steps:

Polling Phase: Get the queue of events and poll the events in the queue;
Check Phase: execute the callback function of
2. setImmediate();
Close Phase: execute the callback function of the
3. close event;
Timers Phase: Execute the callback function called by the
4. setTimeout() and setInterval() functions.

Through this mechanism, Node.js can handle a large number of concurrent requests without blocking threads and maintain a highly efficient running state.

4. Running environment characteristics

Different from the browser environment, Node.js can access underlying system resources, such as file systems and networks, so it has the following characteristics:

Support high-performance I/O operations, such as file reading and writing, network data transmission, etc.;
1. Support non-blocking servers, which can handle a large number of concurrent requests and improve server performance;
2. Supports cross-platform operating environment and can run on multiple operating systems.

In short, the syntax of Node.js has many characteristics, the most common of which are the use of callback functions to handle asynchronous operations, the use of modular programming to manage code, and the single-thread and event loop mechanism to achieve efficient concurrency. Processing, low-level access to system resources supports high-performance I/O, etc. With the widespread application of Node.js in server-side programming, its features have attracted more and more attention and recognition from developers.

The above is the detailed content of What are the characteristics of nodejs syntax?. For more information, please follow other related articles on the PHP Chinese website!