app.js

function App()
{
    var self = this;
    this.complete = 0;
    this.res = '';
    this.pdfToText = function(data){
    var div = document.getElementById('viewer');
    // render the first pages
    var pdf = new PDFJS.PDFDoc(data);
    var total = pdf.numPages;
    
    for (i = 1; i <= total; i++){
      var page = pdf.getPage(i);

      var canvas = document.createElement('canvas');
      canvas.id = 'page' + i;
      canvas.mozOpaque = true;
      div.appendChild(canvas);

      canvas.width = page.width;
      canvas.height = page.height;

      var context = canvas.getContext('2d');
      context.save();
      context.fillStyle = 'rgb(255, 255, 255)';
      context.fillRect(0, 0, canvas.width, canvas.height);
      context.restore();
      
      self.setMessage("Rendering...");
      
      var textLayer = document.createElement('div');
      textLayer.className = 'textLayer';
      document.body.appendChild(textLayer);
      
      page.startRendering(context, function(){
        if (++self.complete == total){
          self.setMessage("Finished rendering. Extracting text...");
          
          window.setTimeout(function()
          {
            var layers = '';
            var nodes = document.querySelectorAll(".textLayer > div");
            for (var j = 0; j < nodes.length; j++)
            {
              layers += nodes[j].textContent + "\n";
            }
            self.res = layers;
            //self.sendOutput(layers);
            self.setMessage("Done!");
          }, 1000);
        }
      }, textLayer);
    }
  };


  this.receiveInput = function(event){
    if (event.source != parent) return;
    if (!event.data.byteLength)
    self.setMessage("Received data");
    self.pdfToText(event.data);
  }

  this.sendOutput = function(text){
    var recipient = parent.postMessage ? parent : (parent.document.postMessage ? parent.document : undefined);
    recipient.postMessage(text, "*");
  };

  this.getRes = function()
  {
    return this.res;
  }
  
  this.setMessage = function(text){
    document.getElementById("message").textContent = text;
  }

  window.addEventListener("message", self.receiveInput, true);
  self.setMessage("Ready");
  self.sendOutput("ready"); 

}