this in Constructor method

newInstance.js

function Person(fn, ln) {
	this.first_name = fn;
	this.last_name = ln;

	this.displayName = function() {
		console.log(`Name: ${this.first_name} ${this.last_name}`);
	}
}

let person = new Person("John", "Reed");
person.displayName();  // Prints Name: John Reed
let person2 = new Person("Paul", "Adams");
person2.displayName();  // Prints Name: Paul Adams