Nodejs implements synchronization

Node.js is a very popular back-end JavaScript running environment that can be used to write high-performance, high-concurrency server-side applications. Although Node.js has many powerful asynchronous programming capabilities, in some cases, synchronous programming may be more suitable for specific scenarios and needs.

1. What is synchronous programming?

Synchronous programming means that the execution of the program is carried out in a certain order. The execution of the code is blocked, and the code will always wait for the completion of certain operations. When encountering an IO operation or network request, the program needs to wait for the operation to complete before continuing. In a single-threaded Node.js application, if an operation is blocked, the performance of the entire application may be affected. Therefore, when writing Node.js applications, asynchronous programming is often adopted to avoid blocking.

2. Advantages of Asynchronous Programming

The main advantage of asynchronous programming is that it can enhance the performance and scalability of the program. Because asynchronous code can execute in parallel, multiple requests can be processed at the same time or multiple tasks can be performed simultaneously, reducing wait time and blocking.

Asynchronous programming also has an important advantage, which is that it can avoid thread synchronization problems caused by multi-threaded programming. In multi-threaded programming, competition between threads can lead to synchronization problems between threads, which makes programs complex and difficult to debug. Since Node.js is single-threaded, competition and synchronization issues between threads are reduced.

3. Applicable scenarios for synchronous programming

Although asynchronous programming is a better choice in most cases, there are some scenarios where synchronous programming may be more suitable. . The following are some scenarios suitable for synchronous programming:

(1) The program needs to perform multiple operations in an orderly manner.

(2) The program needs to wait for the completion of certain operations before executing the next step.

(3) The program needs to obtain the results of multiple operations synchronously.

(4) The program needs to process a large number of calculation operations, not IO operations.

(5) The program needs to ensure the integrity of data and status.

In these cases, synchronous programming can make the code easier to understand and debug, and can make writing the code less difficult.

4. Synchronous programming in Node.js

Although Node.js is the main choice for asynchronous programming, Node.js actually also provides some synchronous programming mechanisms. The following are some methods to implement synchronous programming in Node.js:

(1) Synchronous file reading

In Node.js, files can be read synchronously by using The fs.readFileSync() method can realize synchronous file reading. This method will block the execution of the program before the file reading is completed, and then continue execution until the file reading is completed.

The following is a simple Node.js script used to read a text file and print out the file contents:

const fs = require('fs');

const data = fs.readFileSync('file.txt', 'utf-8');

console.log(data);

The above code uses the method of synchronously reading the file, it will Blocks the execution of the program until the file reading is completed and saves the file contents in the variable data. Then, the program will print out the data.

(2) Execution of synchronous blocking code

In Node.js, you can use the setInterval() function to perform an operation at a fixed time interval. However, the setInterval() function is asynchronous and starts a timer to perform certain operations.

If you want to make the Node.js program pause execution for a period of time, you can use the following code:

function sleep(ms) {
  const start = new Date().getTime();
  while (new Date().getTime() < start + ms);
}

console.log('start');
sleep(5000);
console.log('end');

The above code will cause the Node.js program to pause execution for 5 seconds, and then Continue executing subsequent code. This code uses a sleep function, which blocks the execution of the program for a specified period of time.

(3) Execution of synchronous blocking code (Promise)

In Node.js, we can also use Promise to implement synchronous blocking code execution. Here is an example:

function sleep(ms) {
  return new Promise(resolve => {
    setTimeout(resolve, ms);
  });
}

async function run() {
  console.log('start');
  await sleep(5000);
  console.log('end');
}

run();

The above code uses two functions. The first function sleep() will return a Promise object, which will execute the resolve() callback function within the specified time. The second function run() is an asynchronous function that waits for the Promise object to complete execution during await sleep().

5. Summary

While Node.js is the primary choice for asynchronous programming, there are situations where synchronous programming may be more suitable for certain scenarios and needs. For example, the program needs to perform multiple operations in an orderly manner or needs to wait for the completion of certain operations before proceeding to the next step. Node.js provides some synchronous programming mechanisms, such as synchronous file reading, synchronous blocking code execution, synchronous blocking code execution (Promise), etc. When writing Node.js applications, you need to choose asynchronous or synchronous programming based on the specific scenario to achieve the best performance and scalability.

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