javascript - Where is the property in self-defining function? -

i have question self-defining function.

var scareme = function(){   console.log("boo!");   var instance = this;   scareme = function(){     console.log("double boo!");     return instance;   } } scareme.prototype.nothing = true; var un1 = new scareme(); console.log(un1.nothing); //true scareme.prototype.everything = true; var un2 = new scareme(); console.log(un1 === un2); //true 

it works expected.

console.log(un2.everything); //undefined 

where can 'everything' property?

it won't work because once scareme called, overriding scareme function when try change prototype after initial call changing prototype of second method not first method had created instance. changes prototype not reflected in instance.

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one possible solution override prototype of second object first one

var scareme = function () {     console.log("boo!");     var instance = this,         proto = scareme.prototype;     scareme = function () {         console.log("double boo!");         return instance;     }     scareme.prototype = proto; } scareme.prototype.nothing = true; var un1 = new scareme(); console.log('nothing', un1.nothing); //true scareme.prototype.everything = true; var un2 = new scareme(); console.log(un1 === un2); //true console.log('everything', un1.everything); //true 

demo: fiddle

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another way write same like

var scareme = (function () {     var instance;     return function () {         if (instance) {             return instance;         }         instance = this;      } })(); 

demo: fiddle