old_contents: 'use strict';
  
  var Filter = require('broccoli-filter');
  var LiveScript = require('LiveScript');
  var objectAssign = require('object-assign');
  
  function LiveScriptFilter(inputTree, options) {
    if (!(this instanceof LiveScriptFilter)) {
      return new LiveScriptFilter(inputTree, options);
    }
  
    this.inputTree = inputTree;
    this.options = options || {};
  }
  
  LiveScriptFilter.prototype = Object.create(Filter.prototype);
  LiveScriptFilter.prototype.constructor = LiveScriptFilter;
  
  LiveScriptFilter.prototype.extensions = ['ls'];
  LiveScriptFilter.prototype.targetExtension = 'js';
  
  LiveScriptFilter.prototype.processString = function(str) {
    // LiveScript overwrites the option object.
    return LiveScript.compile(str, objectAssign({}, this.options));
  };
  
  module.exports = LiveScriptFilter;
  
new_contents: 'use strict';
  
  const Filter = require('broccoli-filter');
  const LiveScript = require('LiveScript');
  
  function LiveScriptFilter(inputTree, options) {
    if (!(this instanceof LiveScriptFilter)) {
      return new LiveScriptFilter(inputTree, options);
    }
  
    this.inputTree = inputTree;
    this.options = options || {};
  }
  
  LiveScriptFilter.prototype = Object.create(Filter.prototype);
  LiveScriptFilter.prototype.constructor = LiveScriptFilter;
  
  LiveScriptFilter.prototype.extensions = ['ls'];
  LiveScriptFilter.prototype.targetExtension = 'js';
  
  LiveScriptFilter.prototype.processString = function(str) {
    // LiveScript overwrites the option object.
    return LiveScript.compile(str, Object.assign({}, this.options));
  };
  
  module.exports = LiveScriptFilter;
  
subject: use `const` and Object.assign()