js_inheritance

function shape(){

}
shape.prototype.sayhello = function(){}
function newShape(){

}

// copy prototype 
newShape.prototype = shape.prototype;
newShape.prototype.constructor = newShape
//-----------------------------------------//
function shape(){

}
shape.prototype.sayhello = function(){}
function newShape(){

}
// augmentig prototype 
newShape.prototype = new Shape();
newShape.prototype.constructor = newShape

//-------------------------------------------//
function NEW(O){
  function F(){}
  F.prototype = O.prototype;
  return new f();
}
var obj1= {}
var obj2 = NEW(obj1);
//-----------------------------------------//

var F = function () {};
F.prototype = TwoDShape.prototype;
Triangle.prototype = new F();
Triangle.prototype.constructor = Triangle;