How to synchronize nodejs

Node.js is a very powerful back-end JavaScript running environment that uses a single-threaded event loop mechanism to implement asynchronous programming. However, in some cases, we may need to use synchronous code to avoid the problems caused by asynchrony. So, how do we implement synchronous code in Node.js? Let us find out together below.

1. The concepts of synchronization and asynchronousness

In Node.js, synchronization and asynchronousness are two very important concepts. In synchronous mode, the code will be executed line by line in order, and the next line of code will only continue to be executed after the previous line of code is completed. In asynchronous mode, the code will first register a callback function and then continue to execute the subsequent code. After the operation is completed, execute the callback function. Using asynchronous can greatly improve the efficiency of the code and avoid performance bottlenecks caused by program blocking.

2. How to implement synchronization code

1. Using synchronization API

Node.js provides some synchronization APIs that can help us implement synchronization code. For example, when we use fs.readFileSync to read a file, it will block the execution of the code and will not continue to execute the subsequent code until the file reading is completed.

For example:

const fs = require('fs');
const data = fs.readFileSync('test.txt', 'utf8');
console.log(data);
console.log('读取文件完成');

The above code uses fs.readFileSync to read the file. It will block during the execution of the code. The file content and "read" will not be output until the file reading is completed. "File retrieval completed" message appears.

2. Use async/await to implement synchronous code

async/await is a syntactic sugar for asynchronous programming provided by Es6, which allows us to write asynchronous code in a synchronous manner. Using async/await, we can encapsulate asynchronous operations in a Promise function, use try/catch to handle exceptions, and then use await to wait for the result of the Promise function to return.

For example:

const fs = require('fs');

function readFilePromise() {
  return new Promise((resolve, reject) => {
    fs.readFile('test.txt', 'utf8', (err, data) => {
      if (err) {
        reject(err);
        return;
      }
      resolve(data);
    });
  });
}

async function test() {
  try {
    const data = await readFilePromise();
    console.log(data);
    console.log('读取文件完成');
  } catch (err) {
    console.log(err);
  }
}

test();

The above code uses async/await to read files synchronously. We encapsulate the asynchronous operation in a Promise function readFilePromise and use try/catch to handle exceptions. Inside the test function, we use await to wait for the result of the Promise to return, so that the data variable can be used directly in the subsequent code.

3. Advantages and Disadvantages of Synchronous Code

Using synchronous code can make the code easier to write and debug, and can also ensure the accuracy of the variable access sequence. However, there are some disadvantages to using synchronous code. First, the execution speed of synchronous code is relatively slow because it blocks the execution of the program; secondly, synchronous code may cause excessive resource overhead of the program because it will occupy system resources and memory during code execution.

4. Summary

When using synchronous code in Node.js, we can use the synchronization API provided by Node.js, or we can use syntax sugar such as async/await to achieve it. Using synchronized code can guarantee the order of variable access, but it also brings some disadvantages. In actual development, we need to decide whether to use synchronous code based on specific circumstances.

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