fs模块基础（二）

• createReadStream（从文件流中读取数据，文件大的时候使用）

const fs = require("fs");

const stream = fs.createReadStream("demo.txt");

let str = "";
stream.on("data", chunk => {
  str += chunk;
  console.log(chunk.toString());
});

stream.on("end", _ => {
  console.log(str);
});

stream.on("error", err => {
  console.log(err);
});

• createWriteStream（写入数据）

const data = "我是从数据库中读取到的数据";

const stream = fs.createWriteStream("demo1.txt");

for (var i = 0; i < 100; i++) {
  stream.write(`${data.repeat(3)}${i}\n`, "utf8");
}
stream.end();
stream.on("finish", () => {
  console.log("写入完成");
});
stream.on("error", () => {
  console.log("写入失败");
});

• 管道流

// 创建一个可读流
const readerStream = fs.createReadStream("input.txt");
// 创建一个可写流
const writerStream = fs.createWriteStream("output.txt");

// 管道读写操作
// 读取 input.txt 文件内容，并将内容写入到 output.txt 文件中
readerStream.pipe(writerStream);
console.log("程序执行完毕");