Object.create() vs. new SomeFunction(): When to Use Which JavaScript Object Creation Method?

Understanding the Distinction between Object.create() and new SomeFunction()

JavaScript provides two methods for creating new objects: Object.create() and new SomeFunction(). While they may appear similar at surface level, they exhibit fundamental differences.

Object.create()

Object.create() creates a new object using an existing object as its prototype. This implies that the newly created object inherits properties and methods from the prototype object.

new SomeFunction()

The new operator, followed by a function call, creates a new instance of an object. Unlike Object.create(), it does not establish a prototype chain with the function's prototype property. Instead, the function itself serves as the constructor for the new object, which is returned upon execution.

Differences and Usage Scenarios

Prototypal Inheritance: Object.create() enables prototypal inheritance, allowing objects to inherit behavior and properties from their prototypes. This is useful when creating hierarchies of objects with shared functionality. new SomeFunction() does not create a prototype chain.

Constructor Functions: new SomeFunction() allows the use of constructor functions, which can be used to initialize and configure the newly created object. Object.create() does not provide this facility.

Dealing with Scopes: Object.create() relies on lexical scope, which means that nested functions defined within the prototype object will have access to the outer scope. new SomeFunction() uses block scope, preventing nested functions from accessing the outer scope.

Example

Consider the following code:

var test = {
  val: 1,
  func: function() {
    return this.val;
  }
};

var testA = Object.create(test);

testA.val = 2;
console.log(test.func()); // 1
console.log(testA.func()); // 2

Here, Object.create() is utilized to establish a prototype chain. testA inherits the properties and methods of test.

var otherTest = function() {
  this.val = 1;
  this.func = function() {
    return this.val;
  };
};

var otherTestA = new otherTest();
var otherTestB = new otherTest();
otherTestB.val = 2;
console.log(otherTestA.val); // 1 
console.log(otherTestB.val); // 2

In this example, new SomeFunction() is used to create two instances of the otherTest function. They do not share a prototype chain and are considered distinct objects.

Conclusion

Object.create() and new SomeFunction() serve different purposes in JavaScript. Object.create() establishes prototypal inheritance, while new SomeFunction() allows the use of constructor functions and eliminates the need for an explicit prototype chain. The choice of which method to use depends on the specific requirements and inheritance patterns desired in the application.

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