Obter o conteúdo de um arquivo

Utilitário para obter o conteúdo de um arquivo de um input de tipo file.

/**
 * Get local file content.
 * 
 * @author Bruno Ziiê | eu@brunoziie.com
 */
var FileContent = function(){

 var that = {};

 /**
  * File input Id
  * @type {String}
  */
 that.inputElementId = null

 /**
  * File list from input
  * @type {Object}
  */
 that.fileList = null;

 /**
  * First element of this.fileList
  * @type {Object}
  */
 that.file = null;

 /**
  * FileReader Instance
  * @type {Object}
  */
 that.reader = null;

 /**
  * Object constructor
  *
  * @param {String} inputElementId File Input id
  */
 this.__constructor = function(inputElementId){
  that.inputElementId = inputElementId || null;
  that.reader = new FileReader();
  return this;
 };

 /**
  * Refresh storaged data from input
  * 
  * @return {void}
  */
 that.getElement = function(){
  if(that.inputElementId != null) {
   that.fileList = document.getElementById(that.inputElementId);

   if(that.fileList != null){
    if (that.fileList.files.length > 0) {
     that.file = that.fileList.files[0];
    };
   }
  }
 }

 /**
  * Get the file content in text format
  * 
  * @param  {Function} callback Function to call when the file was loaded
  * @return {void}
  */
 this.getAsText = function(callback){
  that.getElement();

  if(that.file != null){
   var blob = that.file.slice(0, that.file.size);

   that.reader.readAsText(blob);
   that.reader.onloadend = function(){
    callback(that.reader.result);
   }
  }else{
   callback('');
  }
 }

 /**
  * Get the file content in binary format
  * 
  * @param  {Function} callback Function to call when the file was loaded
  * @return {void}
  */
 this.getAsBinary = function(callback){
  that.getElement();

  if(that.file != null){
   var blob = that.file.slice(0, that.file.size);

   that.reader.readAsBinaryString(blob);
   that.reader.onloadend = function(){
    callback(that.reader.result);
   }
  }else{
   callback('');
  }
 }


 /**
  * Get the file content in base64 format
  * 
  * @param  {Function} callback Function to call when the file was loaded
  * @return {void}
  */
 this.getAsBase64Data = function(callback){
  that.getElement();

  if(that.file != null){
   var blob = that.file.slice(0, that.file.size);

   that.reader.readAsDataURL(blob);
   that.reader.onloadend = function(){
    callback(that.reader.result);
   }
  }else{
   callback('');
  }
 }

 return this.__constructor.apply(this, arguments);

};

Uso:

var myFile = new FileContent('arquivo');
myFile.getAsBinary(function(text){
    // fazer algo com o text
});