Understanding Function Declaration, Function Invocation, and Object Instantiation in JavaScript

In JavaScript, functions and objects play a pivotal role in the development of robust applications. The distinction between function Person(){}, var person = Person(), and var person = new Person() might seem subtle, yet it fundamentally affects how your code behaves. MDN’s new operator reference explains what changes when you add new.

Function Declaration: function Person(){}

Using function Person(){} declares a function named Person. This declaration creates a template for an action or object, but does not execute the function nor does it create an instance of an object. It’s akin to defining a recipe without cooking anything.

Function Invocation: var person = Person()

When you invoke a function with var person = Person(), you’re calling the Person function and assigning its return value to the variable person. If the Person function does not explicitly return a value, person will be undefined. Any assignments to this inside Person would also leak onto the global object in non-strict mode, or throw a TypeError in strict mode. This operation executes the function’s code, but it does... premium content.