javascript - How can I use one function for different JS classes? -

assume have 2 classes classa , classb:

function classa(){     this.x = 1;     this.y = 'a';     this.z = false; } 

-

function classb(){     this.x = 0;     this.y = 'b';     this.z = true; } 

and want use 1 function these 2 prototype:

var foo = function(){     if(this.z){          window.alert(this.y + this.x);     } } 

is safe use like

classa.prototype.foo = foo;  classb.prototype.foo = foo; 

because assign same function object different classes.

or there way define interface (like java) , use inheritance somehow?

is safe use like...

yes

this fine. unlike python methods, javascript functions know nothing of class belong to.