class Person { constructor(name) { this.name = name; this.id = Person.nextId++; } } Person.nextId = 0; const jamie = new Person("Jamie"), juliet = new Person("Juliet"), peter = new Person("Peter"), jay = new Person("Jay"); const arr = [jamie, juliet, peter, jay]; // option 1: direct comparison of ID: console.log(arr.find(p => p.id === juliet.id)); // returns juliet object // option 2: using "this" arg: console.log(arr.find(p => p.id === this.id, juliet)); // returns juliet object