When creating JavaScript objects with properties, why is this code necessary?

Question

I am reading about JavaScript prototypes here. Under the Object.create header, some code is written out to illustrate creating objects with prototypes and certain properties:

var person = {
    kind: 'person'
}

// creates a new object which prototype is person
var zack = Object.create(person);

console.log(zack.kind); // => ‘person’

I then encountered this:

var zack = Object.create(person, {age: {value:  13} });
console.log(zack.age); // => ‘13’

Instead of passing {age: {value: 13} }, I passed {age: 13} because it seemed simpler. Unfortunately, a TypeError was thrown. In order to create properties of this object like this, why do we have to pass {age: {value: 13} } rather than just {age: 13}?

InfinitiesLoop · Accepted Answer · 2013-11-25 04:15:07Z

5

Because the parameter is a properties object. You're not just defining fields, you're defining properties which is a bit of a different animal. For example you could specify the 'age' isn't writable. Refer to this documentation:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create

answered Nov 25, 2013 at 4:15

InfinitiesLoop

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