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prototype vs __proto__

Protoype inherientence & __proto__

Ragav Kumar V

Ragav Kumar V

Aug 20, 2022 · 2 min read

prototype vs __proto__

  1. __proto__ refers to the object's friend
  2. kayathri is friend of satya due to setPrototypeOf

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var satya = { eraser: "apsara" };
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var kayathri = { pencil: "camlin", sharper: "natraj" };
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Object.setPrototypeOf(satya, kayathri);
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console.log(satya.pencil);
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// "camlin"
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console.log(kayathri.eraser);
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// undefined

satya.__proto__ (friend) points to kayathri. Moreover, satya can use all keys of kayathri. But, kayathri cannot use keys of satya

An object can have only one friend

  1. satya.__proto__ (friend) points to kayathri
  2. satya can use all keys of kayathri
  3. But kayathri cannot use keys of satya
  4. An object can have only one friend
  5. Object.prototype is common friend of all object

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var satya = { eraser: "apsara" };
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var kayathri = { pencil: "camlin", sharper: "natraj" };
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var badri = { books: ["eng", "tamil", "sci"] };
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Object.setPrototypeOf(satya, kayathri); // satya is friend of kayathri
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Object.setPrototypeOf(kayathri, badri); // kayathri is friend of badri
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// satya -> kayathri -> badri
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console.log(satya.__proto__ === kayathri); // true
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console.log(kayathri.__proto__ === badri); // true
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console.log(kayathri.books);
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// ["eng", "tamil", "sci"]
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console.log(satya.books);
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// ["eng", "tamil", "sci"]


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function Account(name, accno, balance) {
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this.name = name;
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this.accno = accno;
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this.balance = balance;
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this.getBalance = function () {
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return `The balance is: ₹${this.balance}`;
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};
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}
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const ragu = new Account("Ragu", 1000, 1_00_000);
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const mohamed = new Account("Mohamed", 1001, 37_00_000);
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console.log(ragu.getBalance === mohamed.getBalance); // false


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function Account(name, accno, balance) {
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this.name = name;
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this.accno = accno;
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this.balance = balance;
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}
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// Joint family | common friend
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Account.prototype.getBalance = function () {
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return `The balance is: ₹${this.balance}`;
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};
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const ragu = new Account("Ragu", 1000, 1_00_000);
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const mohamed = new Account("Mohamed", 1001, 37_00_000);
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console.log(ragu.getBalance === mohamed.getBalance); // true

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