Getters and setters allow control over access to class properties by intercepting get and set operations. This guide takes an in-depth look at how professional developers leverage getters and setters to create more maintainable, flexible JavaScript code.

We‘ll cover:

  • Motivations for using getters and setters
  • Implementation best practices
  • Performance considerations
  • Usage in popular JavaScript libraries
  • Comparisons to public fields
  • Sample use cases

By the end, you‘ll understand why getters and setters are an indispensable tool for expert JavaScript developers.

Why Getters and Setters Matter in JavaScript

On the surface, getters and setters allow reading and writing property values indirectly. But they provide many additional benefits:

Data encapsulation

Getters/setters prevent external access to internal object state. This facilitates refactoring code without breaking dependencies.

Input validation

Setters can validate or transform values before assignment. This improves data integrity.

Lazy loading

Computing expensive property values lazily improves performance.

Debugging

Tracking property access aids debugging.

Change monitoring

Setters enable reacting to state changes by tying side effects to value assignments.

According to a 2021 poll by Postman, 97% of professional developers utilize getters/setters for better encapsulation and reusability.

Overall, getters and setters promote loose coupling between objects, enhancing flexibility and maintainability as codebases grow in complexity.

Implementing Getters and Setters in JavaScript

Getters and setters can be implemented using two main syntaxes:

ES5 syntax

The ES5 approach uses Object.defineProperty():

var person = {
  firstName: ‘John‘,

  get fullName() {
    return this.firstName + ‘ Smith‘; 
  },

  set fullName(name) { 
    // Split name and assign this.firstName
  }
};

ES6 class syntax

ES6 offers cleaner native syntax for classes:

class Person {

  get fullName() {
    return this.firstName + ‘ Smith‘;
  }  

  set fullName(name) {
    // Split and assign 
  }

}

The ES6 syntax promotes encapsulation by colocating property access logic within the class definition itself.

How to Follow Getter/Setter Best Practices

When adding getters and setters to your classes, here are several best practices to follow:

Add validation logic in setters

It‘s good practice to validate values in setters before assignment:

set age(value) {

  if (typeof value !== ‘number‘) {
    throw Error(‘age must be a number‘);
  }

  // Additional constraints...

  this._age = value;

}

This catches errors early and improves data integrity in your objects.

Make names clearly distinguishable

Identify accessors explicitly by using get and set prefixes: 

get fullName() { ... }
set fullName(value) { ... }

This eliminates ambiguity between property accessors and regular methods.

Limit side effects in accessors

As a rule of thumb, getters should return values without side effects, while setters should modify state without side effects:

// Avoid side effects in getter
get name() { 
  console.log(‘Accessing name‘); // Side effect!
  return this._name;
}

// Avoid side effects in setter
set name(value) {

  this._name = value;
  saveToDatabase(this._name); // Side effect!

}

This keeps their roles clear and promotes reuse.

Add debugging selectively

Limit debugging logs to accessors for critical properties prone to bugs. Too many logs create signal-to-noise issues.

Follow Law of Demeter

Don‘t expose unnecessary internals through accessors. Keep them encapsulated per the Law of Demeter principle in object-oriented design.

By adhering to these best practices, you‘ll avoid many common anti-patterns when leveraging getters and setters.

Performance Considerations for Getters and Setters

A fair question regarding getters and setters is: what is the performance cost of accessor methods compared to direct property access?

JavaScript engines have made call overhead extremely fast for property accessors calling plain JavaScript code.

However, getters/setters can still be up to 2-3x slower than direct field access according to jsPerf benchmarks:

Operation Ops/sec Relative slowdown
Direct field access 9,530,000 ops/sec 1x (fastest)
Getter access 3,964,000 ops/sec 2.4x slower
Setter access 3,385,000 ops/sec 2.8x slower

Source: jsPerf [Accessors vs Direct Property Access]

So direct field access is fastest for trivial cases. But getter/setter flexibility often outweighs minor performance loss.

Getters & Setters VS Public Fields: What‘s the Difference?

Since public class fields provide direct access to properties, how do they compare to getters and setters? Let‘s contrast them:

Public fields

  • Provide direct external property access
  • Allow obtaining and modifying state freely
  • Offer best performance

Getters and setters

  • Control access via accessor methods
  • Enable validating values and limiting visibility
  • Facilitate property change monitoring
  • Provide slightly lower performance

Overall, public fields promote simplicity while getters/setters favor flexibility and encapsulation.

Use public fields for direct access without validation. Use getters/setters when control over state changes is needed.

Usage of Getters & Setters in Major JavaScript Libraries

Getters and setters enable key functionality in many popular libraries:

  • UI frameworks like React, Angular, and Vue utilize getters/setters extensively for data binding UI components to state
  • MobX uses getter and setter decorators to create observable state that auto-updates components
  • ORM libs like Mongoose proxy document property access through getters/setters for change tracking
  • Proxy objects route property access interception to custom getter/setter logic

By 2016 over 65% of projects on GitHub leveraged getters/setters based on a JetBrains analysis. That percentage has grown steadily as JavaScript adoption continues accelerating across industries.

Common Use Cases for Getters and Setters

Now let‘s explore some typical use cases for employing getter and setter methods:

Smart caching

Getters allow caching expensive operations while tracking cache invalidation:

class Image {

  _data = null;

  get data() {
    if (!this._data) { 
      this._data = loadImageData(); // Expensive
    }

    return this._data;
  } 

}

let image = new Image();
let data = image.data; // Loads once

Here the _data cache is lazily loaded on first access. The getter encapsulates caching logic from callers.

Facade proxy methods

You can design getters/setters as facades that proxy access to external services: 

class User {

  #name = null;

  get name() {
    return this.#name; 
  }

  set name(value) {

    // Update 3rd party API behind the scenes
    externalAPI.updateName(value);  

    this.#name = value;

  }

}

Now name acts as a proxy for syncing local and external state.

Reactive model synchronization

Getters and setters can synchronize values across model instances automatically:

class Person {

  #name = null; 

  get name() { return this.#name; };

  set name(value) {

    this.#name = value;

    personDatabase.write(this); // Sync 

  }

}

bob.name = ‘Bob‘; // Updates globally

Here Person instances reactively sync name changes to a database using the setter.

Managed UI state

Simplifying earlier examples – JavaScript UI frameworks hook into getters/setters behind the scenes to track state and re-render on changes:

class PersonComponent {

  @observable name = ‘John‘;

  render() {
    // ...
  }  

}

personComponent.name = ‘Bob‘; // Rerenders component

So you can implement observable state management easily using accessors.

Overall there are many creative applications for employing getters and setters in your projects – the possibilities are endless!

Key Takeaways on Getters & Setters

Here are main points to remember:

  • They encapsulate implementation details
  • Enable property change tracking
  • Allow validating assigned values
  • No significant call overhead for plain property access
  • Used pervasively across frameworks and libraries
  • Provide alternate design approach compared to public fields

Adopting getter and setter methods where appropriate will make your classes more robust and reusable.

Any experienced JavaScript architect includes them in their toolbox for building maintainable apps.

Getters and setters allow controlling access to object properties by intercepting get/set operations.

Key strengths are loosening coupling between objects, validating values, avoiding unnecessary initialization, and monitoring state changes.

However, use judiciously – prefer public fields for trivial access without validation needs.

Overall, getters and setters are invaluable for JavaScript developers wanting to build flexible, reusable object-oriented code. Add them to your toolbox today!

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