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VistasWhy print object display prototype chain not as expected
function F () {
this.a = 1;
this.b = 2;
}
let o = new F(); // {a: 1, b: 2}
// add properties in F function's prototype
F.prototype.b = 3;
F.prototype.c = 4;
console.log(o)
Using Chrome's developer tools, I find the output as follows:
I'm really confused with this output. Who can explain the result.
·
Juan Pablo Isaza
2 Respuestas
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Disclaimer: I am not entirely sure about this answer.
__proto__ refers to the object that is being constructed (it's part of the constructor).
[[Prototype]] is the object that is meant to prototype the current object.
·
Juan Pablo Isaza
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0
[[Prototype]] refers to the internal prototype that every object is created with. It is not accessible, for example
o.prototype.b
returns undefined.
The deprecated __proto__ is initially uncalled, and, when it is called, fills up with the values of [[Prototype]], hence the duplication. So,
o.__proto__.b
returns 3.
The preferred access method is to use the getPrototypeOf() static method of Object.
Object.getPrototypeOf(o).b
returns 3.
·
Juan Pablo Isaza
Denunciar
Responde la pregunta