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I'm trying to understand how to use javascript prototypes and inheritance in Google Apps Script but apparently I'm still missing something.

Here is the structure I'm working on. 

   function Father (  ) {
      this.init.apply ( this, arguments );
    }
    Father.prototype ={
      init: function  (  ) {
        var optns = arguments[0] || {};
        this.job = optns.job || "unemployed";
        this.cars = optns.cars || [];
      }
    }

    function Son (  ) {
      this.init.apply ( this, arguments );
    }
    Son.prototype = {
      init : function  (  ) {
        Father.prototype.init.apply (this, arguments);
        var optns = arguments[0] || {};
        this.computers = optns.tablets || [];
      }
    }

Son differs from Father just for the property to own computers. 

function life() {
 var Tom = new Father({job:'carpenter', cars: ['fiat']});
 var Jim = new Son(Tom);
 Jim.computers.push('iMac');
 Jim.job = 'trader';
 Jim.cars.push('bmw');
 return
 }

Here I want the Son instance Jim to start with the same values as Tom (being a carpenter and owning a fiat) but then, as life goes on, I'm expecting Jim's values to change independently from Tom. In fact, I can add a computer and change job to Jim without affecting Tom but when I add a car to Jim, 'bmw' is also added to Tom's cars. Why???

Note: the code works fine if I replace this line

var Jim = new Son(Tom);

with 

var Jim = new Son({job:'carpenter', cars: ['fiat']})

but I don't get why.

marcomk
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    I digged down the problem, the answer is here... http://stackoverflow.com/questions/6612385/why-does-changing-an-array-in-javascript-affect-copies-of-the-array – marcomk Apr 03 '14 at 13:30
  • Possible duplicate of [Why does changing an Array in JavaScript affect copies of the array?](https://stackoverflow.com/questions/6612385/why-does-changing-an-array-in-javascript-affect-copies-of-the-array) – Sunny Patel May 01 '18 at 17:44

0 Answers0