anchor.diff:  
   ```javascript
   var glob = require('glob');
  -var asciidoctor = require('asciidoctor.js')();
  -
  -var processor = asciidoctor.Asciidoctor();
  +var processor = require('asciidoctor.js')();
   
   glob('documentation/*.adoc', function (err, files) { // <1>
  -  files.each(function(file) {
  +  files.forEach(function(file) {
       processor.convertFile(file); // <2>
     });
   });
  
positive.code: [source,javascript]
  ----
  var content = '== Title';
  var doc = Opal.Asciidoctor.load(content);
  doc.setAttribute('data-uri', 'true');
  console.log(doc.getAttribute('data-uri')); // prints 'true'
  
  
negative.code: [source,javascript]
  ----
  var content = '== Title';
  var doc = processor.load(content);
  console.log(doc.getAttribute('data-uri')); // prints undefined
  console.log(doc.getAttribute('data-uri', 'false')); // prints 'false'
  
  