Object.create( parentObject{ nestedObject:{} } )

Question

With reference to Sam Elsamman's post, I'm enquiring if you have written a function which gives the expected behaviour to Object.create() please?

var animal = {traits: {}};            // a nested object as parent
var lion = Object.create(animal);
var bird = Object.create(animal);
lion.traits.legs = 4;
bird.traits.legs = 2;

console.log(lion.traits.legs);        // 2

// edited following adiga's comment:`
animal.traits.hasOwnProperty("legs"); // true

I expect:

// edited following adiga's comment:
console.log(lion.traits.legs);        // 4
animal.traits.hasOwnProperty("legs"); // false

Cheers

lion and bird share the same [[Prototype]]. So, adding a property to traits updates the same animal object. — adiga
– adiga, Commented Nov 25, 2019 at 7:26
Also, why do you expect lion.hasOwnProperty("legs") to return true? Even if you did lion.traits = { legs: 4 }, it will still return false for lion.hasOwnProperty("legs") — adiga
– adiga, Commented Nov 25, 2019 at 7:30
adiga: I was wrong, you're right: it will still return false for lion.hasOwnProperty("legs") — Rich
– Rich, Commented Nov 25, 2019 at 7:36

Singhi John · Accepted Answer · 2019-11-25 07:44:04Z

1

const create = (proto) => {
  const o = {}
  o.__proto__ = proto
  Object.keys(proto).forEach(key => {
    const val = proto[key]
    if (typeof val === 'object')
       o[key] = Object.assign({}, val)
    else
       o[key] = val
  })
  return o
}

answered Nov 25, 2019 at 7:44

Singhi John

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Suhag Lapani · Accepted Answer · 2019-11-25 07:26:17Z

1

var animal = {traits: {}};            // a nested object as parent
var lion = Object.create(JSON.parse(JSON.stringify(animal)));
var bird = Object.create(JSON.parse(JSON.stringify(animal)));
lion.traits.legs = 4;
bird.traits.legs = 2;

console.log(lion.traits.legs);        
lion.hasOwnProperty("legs");         
animal.traits.hasOwnProperty("legs");

answered Nov 25, 2019 at 7:26

Suhag Lapani

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1 Comment

adiga Over a year ago

@Rich Note that, if there are any functions in animal, it will removed by JSON.stringify(). I think lion.traits = { legs: 4 } is a better option

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