使用 Node.js 读取文件

¥Reading files with Node.js

在 Node.js 中读取文件的最简单方法是使用 fs.readFile() 方法,向其传递文件路径、编码和将使用文件数据(和错误)调用的回调函数:

¥The simplest way to read a file in Node.js is to use the fs.readFile() method, passing it the file path, encoding and a callback function that will be called with the file data (and the error):

const fs = require('node:fs');

fs.readFile('/Users/joe/test.txt', 'utf8', (err, data) => {
  if (err) {
    console.error(err);
    return;
  }
  console.log(data);
});

或者,你可以使用同步版本 fs.readFileSync()

¥Alternatively, you can use the synchronous version fs.readFileSync():

const fs = require('node:fs');

try {
  const data = fs.readFileSync('/Users/joe/test.txt', 'utf8');
  console.log(data);
} catch (err) {
  console.error(err);
}

你还可以使用 fs/promises 模块提供的基于 promise 的 fsPromises.readFile() 方法:

¥You can also use the promise-based fsPromises.readFile() method offered by the fs/promises module:

const fs = require('node:fs/promises');

async function example() {
  try {
    const data = await fs.readFile('/Users/joe/test.txt', { encoding: 'utf8' });
    console.log(data);
  } catch (err) {
    console.log(err);
  }
}
example();

fs.readFile()fs.readFileSync()fsPromises.readFile() 三个都在返回数据之前读取内存中文件的全部内容。

¥All three of fs.readFile(), fs.readFileSync() and fsPromises.readFile() read the full content of the file in memory before returning the data.

这意味着大文件将对内存消耗和程序执行速度产生重大影响。

¥This means that big files are going to have a major impact on your memory consumption and speed of execution of the program.

在这种情况下,更好的选择是使用流读取文件内容。

¥In this case, a better option is to read the file content using streams.