vm.js

var vm = require('vm');
var boss = 'Mr. Trump'
  , condition = 'bald';


var script = [
  'boss = name;',
  'condition = type;',
  'result = boss + " is " + condition;'
].join('\n');

var ctx = {
  name: 'Dan',
  type: 'awesome'
};

var evaled = vm.runInContext(script, vm.createContext(ctx));
console.log(evaled);
// Dan is awesome

ctx = {
  name: boss,
  type: condition
};

var evaled = vm.runInContext(script, vm.createContext(ctx));
console.log(evaled);
// Mr. Trump is bald