JavaScript Internals (521 Qs)•Part 4: Prototypes, Object Methods & Event Loop (174 - 253)
What is the difference between proto and prototype
The __proto__ object is the actual object that is used in the lookup chain to resolve methods, etc. Whereas prototype is the object that is used to build __proto__ when you create an object with the new operator (a special variant of a function call).
javascript
new Employee().__proto__ === Employee.prototype;
new Employee().prototype === undefined;
There are few more differences,
| feature | Prototype | proto |
|---|---|---|
| Access | All function constructors have prototype properties. | All objects have __proto__ property |
| Purpose | Used to reduce memory wastage with a single copy of function | Used in lookup chain to resolve methods, constructors etc. |
| ECMAScript | Introduced in ES6 | Introduced in ES5 |
| Usage | Frequently used | Rarely used |