CODEWITHSUNDEEP
javascriptconstructorprototype
jason
jason

Reputation: 1631

prototype and constructor property in JS

Code snippet is following, Can anyone explain why a.hasOwnProperty("prototype") is true, the others are false? Does it mean function has its own prototype, the others are inherited from Object?If so, why c.hasOwnProperty("prototype") is false? Besides, where does property of their constructor property come from? Thanks

    var a = function () {
    };
    var b = new String("test");
    var c = {};

    console.log(a.hasOwnProperty("prototype"));//true
    console.log(b.hasOwnProperty("prototype"));//false
    console.log(c.hasOwnProperty("prototype"));//false
    console.log(a.hasOwnProperty("constructor"));//false
    console.log(b.hasOwnProperty("constructor"));//false
    console.log(c.hasOwnProperty("constructor"));//false
    console.log(a.constructor);//Function()
    console.log(b.constructor);//String()
    console.log(c.constructor);//Object()

Upvotes: 1

Views: 406

Answers (1)

Michiel Overeem
Michiel Overeem

Reputation: 3992

The prototype property is only available on a constructor function. 'a' is a function and thus has a prototype. 'b' and 'c' are instances. They do not have prototypes, their constructors have prototypes:

console.log(a.constructor.hasOwnProperty("prototype")) // true
console.log(b.constructor.hasOwnProperty("prototype")) // true
console.log(c.constructor.hasOwnProperty("prototype")) // true

Upvotes: 3

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