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()
和 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.