JavaScript method of object not working -

i'm trying create simple object method changes value of 1 of keys. want initialize isfoodwarm key false, output value, change true, output again. expected output false , true, method should change true, getting error. tried removing parentheses mybreakfast.heat();, got rid of error, didn't change value. doing wrong? here code.

function breakfast(food, drink, isfoodwarm) {     this.food = food,     this.drink = drink,     this.isfoodwarm = isfoodwarm,     heat = function() {         if (isfoodwarm === false){             isfoodwarm = true;             console.log("your food warm");         }     }  }  var mybreakfast = new breakfast("english muffin", "oj", "false");  console.log(mybreakfast.isfoodwarm); mybreakfast.heat(); console.log(mybreakfast.isfoodwarm); 

i following console output:
false
uncaught typeerror: mybreakfast.heat not function

you need attach heat method constructor breakfast too. , isfoodwarm property must accessed using this.isfoodwarm inside heat method.

this.heat=function() {     if (this.isfoodwarm === false){         this.isfoodwarm = true;         console.log("your food warm");     } } 

explanation : without this operator heat method gets attached global object, when call mybreakfast.heat gives uncaught typeerror because defined under window.heat.

note : when need pass boolean don't wrap inside quotes change boolean string behave true.

so change constructor call

new breakfast("english muffin", "oj", false);  \\remove double quotes around false 

demo

function breakfast(food, drink, isfoodwarm) {      this.food = food,      this.drink = drink,      this.isfoodwarm = isfoodwarm,      this.heat = function() {          if (this.isfoodwarm === false){              this.isfoodwarm = true;              console.log("your food warm");          }      }    }    var mybreakfast = new breakfast("english muffin", "oj", false);    console.log(mybreakfast.isfoodwarm);  mybreakfast.heat();  console.log(mybreakfast.isfoodwarm);