javascript - How can you call a variable in a method from within the object? -

i'm trying learn oop in javascript.

i made following code supposed return time spent in mailthread:

function mailthread(url) {     this.timerison = true;     this.c = 0;     this.url = url;     this.timercounter = function () {         if(this.timerison) { //doesnt called??             console.log('timerison');             this.c = this.c + 1;             console.log(this.c);         } else {             this.windowtimeopen = this.c         }     }     this.timerinterval = setinterval(this.timercounter, 1000); }  mailthread1 = new mailthread('test'); 

however this.timerison seems return undefined preventing timer running. doing wrong here?

also tested in following fiddle: http://jsfiddle.net/b5vt5/

the problem within scope of function called timercounter, "this" refers function itself. this:

function mailthread(url) {     var self = this;     self.timerison = true;     self.c = 0;     self.url = url;     self.timercounter = function () {     if (self.timerison) { //using self instead of         console.log('timerison');         self.c=this.c+1;         console.log(self.c);     } else {     self.windowtimeopen = self.c     }     }     self.timerinterval = setinterval(self.timercounter,1000); }  mailthread1 = new mailthread('test'); 

i recommend @ mdn introduction oop