计算转换流中的行数。节点js

const { Transform } = require('stream');

class LineCounter extends Transform {
  constructor(options) {
    super(options);
    this.lineCount = 0;
  }

  _transform(chunk, encoding, callback) {
    const lines = chunk.toString().split('\n');
    this.lineCount += lines.length - 1; // 减去最后一行的换行符
    this.push(chunk);
    callback();
  }

  _flush(callback) {
    // 可以在这里进行最后的处理操作
    callback();
  }
}

// 使用示例
const fs = require('fs');
const readStream = fs.createReadStream('input.txt');
const lineCounter = new LineCounter();

readStream.pipe(lineCounter);

lineCounter.on('finish', () => {
  console.log('行数：', lineCounter.lineCount);
});