text: 
      var api = fretboardApi;
  
      /*
      function stringify(o) {
          return JSON.stringify(o, function(k,v) { return v instanceof Array ? JSON.stringify(v) : v }, 2)
              .replace(/"\[/g, '[')
              .replace(/\]"/g, ']')
              .replace(/\\"/g, '"')
              .replace(/""/g, '"');
      }
      */
  
      // https://davidwalsh.name/detect-native-function
  
      // Used to resolve the internal `[[Class]]` of values
      var toString = Object.prototype.toString;
  
      // Used to resolve the decompiled source of functions
      var fnToString = Function.prototype.toString;
  
      // Used to detect host constructors (Safari > 4; really typed array specific)
      var reHostCtor = /^\[object .+?Constructor\]$/;
  
      // Compile a regexp using a common native method as a template.
      // We chose `Object#toString` because there's a good chance it is not being mucked with.
      var reNative = RegExp('^' +
          // Coerce `Object#toString` to a string
          String(toString)
          // Escape any special regexp characters
              .replace(/[.*+?^${}()|[\]\/\\]/g, '\\$&')
              // Replace mentions of `toString` with `.*?` to keep the template generic.
              // Replace thing like `for ...` to support environments like Rhino which add extra info
              // such as method arity.
              .replace(/toString|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$'
      );
  
      function isNative(value) {
          var type = typeof value;
          return type == 'function'
              // Use `Function#toString` to bypass the value's own `toString` method
              // and avoid being faked out.
              ? reNative.test(fnToString.call(value))
              // Fallback to a host object check because some environments will represent
              // things like typed arrays as DOM methods which may not conform to the
              // normal native pattern.
              : (value && type == 'object' && reHostCtor.test(toString.call(value))) || false;
      }
  
      function printObj(o) {
          if (isNative(o.toString)) {
              document.write(`<div class="code result">${JSON.stringify(o, null, 2)}</div>`);
          } else {
              document.write(`<div class="code result">${o.toString()}</div>`);
          }
      }
  