Node.js:不可能在全局变量中使用回调结果？

Question

我知道这个问题已经被问了很多次了，但是现在我已经用了19.5个小时在这个问题上没有任何结果，我不能指望我自己能做到这一点。我在网上到处搜索指南和小贴士，但这似乎是不可能的。我尝试过承诺和一切，但这是行不通的。

百万互联网络给帮手。

我到底想做什么？

我的script(auto.js)用Tesseract读取图片(其中包含文本"A“或"B")，然后使用脚本中的结果文本作为全局变量来检查对象数组中的数字，并执行其他操作(在节点-tesseract中我不能这样做)，但我不能做任何事情，但只能将结果记录在控制台上。如果我尝试以其他方式访问它，它就不会让我这样做。

对于beta测试，我只在提示符下运行代码(“节点自动”)。

AUTO.JS：

调用node-tesseract模块的auto.js具有：

var tesseract = require('node-tesseract');

auto.js收到Tesseract的结果，并用JQuery将其转换为数字：

    require("jsdom").env("", function(err, window) {
        var $ = require("jquery")(window);

// Char is Tesseract's result, let's convert it to numbers.

               var charNums = [
           { char: 'A', nums: '1234'}, 
           { char: 'B', nums: '5678'}
        ];

        function getNum(char)
    {
        var result = null;
        var chars = $.grep(charNums, function(e){ return e.char === char; });
                if (chars.length == 0) {
          // not found
        } else {
                result = chars[0].nums;
        }
                return result;
        }

// 2.jpg is the character's picture, let's convert it to text.

        tesseract.process('2.jpg', function(err, text) {
                var foo = "asd"; // For a test.
                foo = "bef"; // For a test.

                console.log("1: "+foo); // This works.
                console.log("2: "+text); // This works.

                foo = ""+text; // For a test.
                console.log("3: "+foo); // This works.

                foo = ""+getNum(text); //Important.
                console.log("4: "+foo); //This does not work.
        });

    });

TESSERACT.JS

'use strict';

/**
 * Module dependencies.
 */
var utils = require('./utils');
var exec = require('child_process').exec;
var fs = require('fs');
var tmpdir = require('os').tmpdir(); // let the os take care of removing zombie tmp files
var uuid = require('node-uuid');
var path = require('path');
var glob = require("glob");

var Tesseract = {

  tmpFiles: [],

  /**
   * options default options passed to Tesseract binary
   * @type {Object}
   */
  options: {
    'l': 'eng',
    'psm': 10,
    'config': null,
    'binary': 'tesseract'
  },

  /**
   * outputEncoding
   * @type {String}
   */
  outputEncoding: 'UTF-8',

  /**
   * Runs Tesseract binary with options
   *
   * @param {String} image
   * @param {Object} options to pass to Tesseract binary
   * @param {Function} callback
   */
  process: function(image, options, callback) {

    if (typeof options === 'function') {
      callback = options;
      options = null;
    }

    options = utils.merge(Tesseract.options, options);

    // generate output file name
    var output = path.resolve(tmpdir, 'node-tesseract-' + uuid.v4());

    // add the tmp file to the list
    Tesseract.tmpFiles.push(output);

    // assemble tesseract command
    var command = [options.binary, image, output];

    if (options.l !== null) {
      command.push('-l ' + options.l);
    }

    if (options.psm !== null) {
      command.push('-psm ' + options.psm);
    }

    if (options.config !== null) {
      command.push(options.config);
    }

    command = command.join(' ');

    var opts = options.env || {};

    // Run the tesseract command
    exec(command, opts, function(err) {
      if (err) {
        // Something went wrong executing the assembled command
        callback(err, null);
        return;
      }

      // Find one of the three possible extension
      glob(output + '.+(html|hocr|txt)', function(err, files){
        if (err) {
          callback(err, null);
          return;
        }
        fs.readFile(files[0], Tesseract.outputEncoding, function(err, data) {
          if (err) {
            callback(err, null);
            return;
          }

          var index = Tesseract.tmpFiles.indexOf(output);
          if (~index) Tesseract.tmpFiles.splice(index, 1);

          fs.unlink(files[0]);

            callback(null, data)
        });
      })
    }); // end exec

  }

};

function gc() {
  for (var i = Tesseract.tmpFiles.length - 1; i >= 0; i--) {
    try {
      fs.unlinkSync(Tesseract.tmpFiles[i] + '.txt');
    } catch (err) {}

    var index = Tesseract.tmpFiles.indexOf(Tesseract.tmpFiles[i]);
    if (~index) Tesseract.tmpFiles.splice(index, 1);
  };
}

var version = process.versions.node.split('.').map(function(value) {
  return parseInt(value, 10);
});

if (version[0] === 0 && (version[1] < 9 || version[1] === 9 && version[2] < 5)) {
  process.addListener('uncaughtException', function _uncaughtExceptionThrown(err) {
    gc();
    throw err;
  });
}

// clean up the tmp files
process.addListener('exit', function _exit(code) {
  gc();
});

/**
 * Module exports.
 */
module.exports.process = Tesseract.process;
    });

Answer 1

更新的代码/现在正在工作

      var getChar = function(callback) {
            tesseract.process('2.jpg', function(err, text) {
                    var foo = "asd"; // For a test.
                    foo = "bef"; // For a test.

                    console.log("1: "+foo); // This works.
                    console.log("2: "+text); // This works and gives right result. Why only this?

                text = text.trim();
                text = text.toUpperCase();

                callback(text);
            });
      };
      var getNums = function (callback) {
    getChar(function(data){
        /* This data stack 2  */
        callback(data);
    });
};

function getNum(){
    getNums(function(data){
        var $ = require("jquery")(window);
               var charNums = [
       { char: 'A', nums: '1234'}, 
       { char: 'B', nums: '2345'}, 
       { char: 'C', nums: '3456'}, 
       { char: 'D', nums: '4567'}, 
       { char: 'E', nums: '5678'}, 
       { char: 'F', nums: '6789'}, 
       { char: 'G', nums: '7890'}, 
       { char: 'H', nums: '0987'}, 
       { char: 'J', nums: '8765'}, 
       { char: 'K', nums: '7654'}, 
       { char: 'L', nums: '6543'}, 
       { char: 'M', nums: '5432'}, 
       { char: 'N', nums: '4321'}, 
       { char: 'P', nums: '3210'}, 
       { char: 'R', nums: '2109'}, 
       { char: 'S', nums: '1098'}
    ];
                 var chars = $.grep(charNums, function(e){ return e.char === data; });
                if (chars.length == 0) {
        } else {
                var result = chars[0].nums;
        }
        console.log("Character: ", data);
        console.log("Number:", result);
// DO SOMETHING
    });
}
getNum();