如何将所有这些节点代码转换为承诺

Question

我使用以下代码，我想将其转换为承诺，所以我已经开始承诺子进程，但我的问题是如何将所有转换为承诺， 我需要将代码划分为其他（参见 cmets）方法 当我按原样使用代码时，它的工作正常。

var Promise = require('bluebird'),
    fs = require('fs').


module.exports = {
    createNew: function () {
        fs.readFile("c://test.txt", 'utf8', function (err, data) {
            if (err) {
                return console.log(err);
            }

            // 1. from Here to needed to divide to new method
            //    which just return cmd value

            var fileKeyValObj = {};
            data.split("\n").forEach(function (element) {
                var sep = element.indexOf(':');

            });

            var cmd = fileKeyValObj['name'];

            // 2. this code should be in additional method

            if (typeof cmd !== 'undefined') {
                var exec = Promise.promisify(require('child_process').exec);
                var childProcess = exec(cmd).spread(function (stdout, stderr) {

                }).catch(function (error) {
                    console.log(error)
                });

            }
        });
    },
}

Answer 1

您可以在 fs 上使用 bluebird .promisifyAll() 函数以及您的 exec 命令，然后将它们链接在一起：

var Promise = require('bluebird');
var fs = Promise.promisifyAll(require('fs'));
var exec = Promise.promisify(require('child_process').exec);


var parseFile = function(data) {
  var fileKeyValObj = {};

  data.split('\n').forEach(function (element) {
      var sep = element.indexOf(':');
      var cmdValue = element.substring(sep + 2);
      fileKeyValObj[element.substr(3, sep)] = cmdValue;
  });

  return fileKeyValObj['name'];
};


module.exports = {
  createNew: function () {
    return fs.readFileAsync('c://test.txt', 'utf8')
      .then(parseFile)
      .then(exec)
      .spread(function(stdout, stderr) {
        // do stuff here with stdout and stderr

        if (stderr) {
          throw new Error('An Error Occurred.');
        }

        // anything returned will be returned on the next item in the chain.
        return stdout;
      });
    },
};

如何从另一个模块调用函数：

var myModule = require('./path/to/module');

myModule.createNew().then(function(data) {
  // this is the data returned from the final step of the createNew promise chain.
  console.log(data);
}).catch(function(err) {
  // catch and handle errors here instead.
  console.error(err);
});

Answer 2

你应该在fs上使用Promise.promisifyAll。

import Promise from 'bluebird'

let fs = Promise.promisifyAll(require('fs'))
let exec = Promise.promisify(require('child_process').exec)

function mapCommands (file) {
    return file.split('\n').reduce((p, c) => {
        let separation = c.indexOf(':')
        p[c.slice(3, separation)] = c.slice(separation + 2)
        return p
    }, {})    
}

function execCommands (obj) {
    let commands = []
    for (let key in obj) {
        let cmd = exec(obj[key])
        commands.push(cmd)
    }
    return Promise.all(commands)
}

export default {
    createNew () {
        fs.readFileAsync('C://test.txt', 'utf8')
        .then(mapCommands)
        .then(execCommands)
        .then(() => {
            // success; all commands executed
        }).catch((err) => {
            console.log(err)    // handle err
        }) 
    }
}