Getters and setters

To assign a value to a property of a JavaScript object is as simple as:

var myObj = {
  prop: 'Hello'
}

To retrieve it is just as simple:

myObj.prop

There's no trick here. The point I want to make though, is that we can replace this normal assignment/retrieval mechanism of an object through use ofgetters and setters. These are special functions that allow custom logic for getting or setting the property's value.

Getters and setters are especially useful when one property's value is determined by another. Here's an example:

var person = {
  firstName: 'Abraham',
  lastName: 'Lincoln',
  get fullName() {
    return this.firstName + ' ' + this.lastName;
  },
  set fullName(name) {
    var words = name.toString().split(' ');
    this.firstName = words[0] || '';
    this.lastName = words[1] || '';
  }
}

Thegetandsetfunctions of thefullNamepropertyare invoked whenever we attempt a normal assignment/retrieval of its value:

console.log(person.fullName); // Abraham Lincoln
person.fullName = 'George Washington';
console.log(person.firstName); // George
console.log(person.lastName) // Washington