Question

我无法让许多异步操作流向右流。正如下面的代码所示，names首先打印到控制台，然后打印years和in readFile，然后打印readFile，当我＆＃39; d喜欢之前发生的整个forEach / const fs = require('fs') const names = {} const years = {} fs.readdir('./namesData', (err, files) => { files.forEach(file => { var year = file.substr(3, 4) var yearObj = {} fs.readFile(`./namesData/${file}`, 'utf8', (err, data) => { console.log('in readFile') if (err) throw new Error(err) var arr = data.split('\n') arr.forEach(record => { var recordArray = record.trim().split(',') var name = recordArray[0] var gender = recordArray[1] var score = recordArray[2] // populate 'names' object var nameObj = {year: year, gender: gender, score: score} if (names.hasOwnProperty(name)) { names[name].push(nameObj) } else { names[name] = [nameObj] } // populate 'years' object & add to yearObj and then years object var yearNameObj = {gender: gender, score: score} if (yearObj.hasOwnProperty(name)) { yearObj[name].push(yearNameObj) } else { yearObj[name] = [yearNameObj] } }) }) console.log('outside readFile') years[year] = yearObj }) console.log(names) console.log(years) })处理。

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Answer 1

我试过这种方法。似乎足以满足您在循环后打印names，years的需要。

'use strict';

let _ = require('lodash');
const fs = require('fs');

function readFile(file) {
  try {
    console.log('in readFile');
    return fs.readFileSync(`./namesData/${file}`, 'utf-8');
  } catch (err) {
    console.log('err ', err.stack);
    return '';
  }
}

fs.readdir('./namesData', (err, files) => {
  let details = _.map(files, (file) => {
    let data = readFile(file);
    let year = file.substr(3, 4);
    return _.map(data.split('\n'), (row) => {
      if (_.isEmpty(row)) {
        return;
      }
      let words = row.trim().split(',');
      return {
        year: year,
        name: words[0],
        gender: words[1],
        score: words[2]
      };
    });
  });
  console.log('names', _.groupBy(details, 'name'));
  console.log('years', _.groupBy(details, 'year'));
});

使用硬编码的details数组

进行测试

let details = [{
  year: 1998,
  name: 'A',
  gender: 'M',
  score: 20
}, {
  year: 1998,
  name: 'B',
  gender: 'M',
  score: 21
}, {
  year: 1999,
  name: 'A',
  gender: 'M',
  score: 100
}, {
  year: 1999,
  name: 'A',
  gender: 'M',
  score: 80
}];

如何使用Node fs构建异步流

1 个答案: