javascript - JSON parse error: Cannot read property -

i have created little jt code, gives me error

function mind(){     var request = "request";     var reply = "reply";     var words = '';      this.reply = function(){         if(request == words.nouns[0].noun){             reply = words.nouns[0].noun;         }         else             reply = this.words.nouns[0].noun;     }      this.setrequest = function(req){         request = req;     }      this.getreply = function(){         return reply;     }      this.parse = function(u){         var xmlhttp = new xmlhttprequest();         var url = u;         var result;         xmlhttp.onreadystatechange = function() {             if (xmlhttp.readystate == 4 && xmlhttp.status == 200) {                 words = json.parse(xmlhttp.responsetext);             }         }         xmlhttp.open("get", url, true);         xmlhttp.send();         return result;     }      this.construct = function(){         words = this.parse('mind/words.json');     }}      var mind = new mind();     mind.parse('mind/words.json'); 

and here json file

{     "nouns": [         {"noun": "child"},         {"noun": "father"}     ] } 

in command live goes well, when run code, appears error

uncaught typeerror: cannot read property 'nouns' of undefined

mutliple errors. fundamental 1 code ignores xmlhttprequest async, , wont return value in same way "regular" functions. read here: how make function wait until callback has been called using node.js. tl;dr have to pass in "callback-function" parse-method , "return" value using function, instead of using return-statement. google "javascript callbacks" , read few tutorials if concept new you!

you have minor errors, returning result parse, never setting result anything. words being assigned in multiple places in way doesn't make sense. both of these things go away when solve sync/async issues.

edit:

essentially fix looks this:

this.parse = function(u, callback){ // "callback" new     var xmlhttp = new xmlhttprequest();     var url = u;     var result;     xmlhttp.onreadystatechange = function() {         if (xmlhttp.readystate == 4 && xmlhttp.status == 200) {             words = json.parse(xmlhttp.responsetext);             callback(null, words); // we're "returning" words here         }     }     xmlhttp.open("get", url, true);     xmlhttp.send();     // no return statement here! }  this.construct = function(){     this.parse('mind/words.json', function(error, words) {         // here can use words!     }); }}