Ultimate Guide to Getters and Setters in JavaScript

Getters and setters are functions or methods used to get and set a values of variables. The getter-setter judgment is common in computer programming: roughly all high-level programming languages come with a set of syntax to exercise getters and setters, including JavaScipt.

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In this post, we’ll see what getters setters are, and how to create and use them in JavaScript.

Getters-setters and encapsulation

The thought of getters and setters is always mentioned in and with encapsulation. Encapsulation can be understood in dual ways.

Firstly, it is a environment adult of a data–getters–setters contingent to entrance and cgange that data. This clarification is useful when some operations, such as validation, have to be performed on a data before saving or observation it—getters and setters yield a ideal home for it.

Secondly, there’s a stricter clarification according to that encapsulation is finished to hide data, to make it untouched from other code, except by a getters and setters. This approach we don’t finish adult accidentally overwriting critical data with some other formula in a program.

Create getters and setters

1. With methods

Since getters and setters are basically functions that fetch/change a value, there are more than one ways to emanate and use them. The initial approach is:

var obj = {
  foo:    'this is a value of foo',
  getFoo: function() {
            lapse this.foo;
        },
  setFoo: function(val) {
            this.foo = val;
        }
}

console.log(obj.getFoo());
// "this is a value of foo"

obj.setFoo('hello');

console.log(obj.getFoo());
// "hello"

This is the simplest way to emanate getters and setters. There’s a skill foo and there are dual methods: getFoo and setFoo to return and allot a value to that property.

2. With keywords

A some-more “official” and strong approach of formulating getters and setters is by regulating a get and set keywords.

To create a getter, place a get keyword in front of a duty stipulation that will offer as a getter method, and use a set keyword in a same approach to create a setter. The syntax is as follows:

var obj = {
  fooVal: 'this is a value of foo',
  get foo() {
      lapse this.fooVal;
  },
  set foo(val) {
      this.fooVal = val;
  }
}

console.log(obj.foo);
// "this is a value of foo"

obj.foo = 'hello';

console.log(obj.foo);
// "hello"

Note that a information can usually be stored underneath a skill name (fooVal) that’s different from a name of a getter-setter methods (foo) since a skill holding a getter-setter can’t reason a data as well.

Which approach is better?

If we select to emanate getters and setters with keywords, we can use a assignment user to set a data and a dot user to get a data, a same approach you’d access/set a value of a unchanging property.

However, if we select a initial approach of coding getters and setters, we have to call a setter and getter methods using a duty call syntax since they are standard functions (nothing special like those combined regulating a get and set keywords).

Also, there’s a possibility we competence finish adult incidentally assigning some other value to a properties that hold those getter-setter methods and lose them completely! Something we don’t have to worry about in a after method.

So, we can see because we pronounced a second technique is some-more robust.

Overwrite prevention

If for some reason we cite a initial technique, make a properties holding a getter-setter methods read-only by formulating them using Object.defineProperties. Properties combined around Object.defineProperties, Object.defineProperty and Reflect.defineProperty automatically configure to writable: false that means read-only:

/* Overwrite impediment */
var obj = {
  foo: 'this is a value of foo'
};

Object.defineProperties(obj, {
  'getFoo': {
      value: duty () {
          lapse this.foo;
      }
  },
  'setFoo': {
      value: duty (val) {
          this.foo = val;
      }
  }
});

obj.getFoo = 66;
// getFoo is not going to be overwritten!

console.log(obj.getFoo());
// "this is a value of foo"

Operations inside getters and setters

Once you’ve introduced a getters and setters, we can go forward and perform operations on a data before changing or returning it.

In a formula below, in a getter duty a information is concatenated with a string before being returned, and in a setter duty a validation of whether a value is a array or not is achieved before updating n.

var obj = {
  n: 67,
  get id() {
      lapse 'The ID is: ' + this.n;
  },
  set id(val) {
      if (typeof val === 'number')
          this.n = val;
  }
}

console.log(obj.id);
// "The ID is: 67"

obj.id = 893;

console.log(obj.id);
// "The ID is: 893"

obj.id = 'hello';

console.log(obj.id);
// "The ID is: 893"

Protect information with getters and setters

So far, we lonesome a use of getters and setters in a initial context of encapsulation. Let’s pierce on to a second, i.e. how to hide information from outward code with a assistance of getters and setters.

Unprotected data

The environment adult of getters and setters doesn’t meant a information can usually be accessed and altered around those methods. In a following example, it’s changed directly though touching a getter and setter methods:

var obj = {
  fooVal: 'this is a value of foo',
  get foo() {
      lapse this.fooVal;
  },
  set foo(val) {
      this.fooVal = val;
  }
}

obj.fooVal = 'hello';

console.log(obj.foo);
// "hello"

We didn’t use a setter though directly altered a information (fooVal). The information we primarily set inside obj is left now! To forestall this from duty (accidentally), we need some protection for your data. You can supplement that by limiting a scope of where your information is available. You can do that by possibly block scoping or function scoping.

1. Block scoping

One approach is to use a retard scope inside that a information will be tangible regulating a let keyword that limits a scope to that block.

A block scope can be combined by fixation your formula inside a span of curly braces. Whenever we emanate a retard range make certain to leave a comment above it seeking for a braces to be left alone, so that no one removes a braces by mistake meditative they are some additional surplus braces in a formula or add a label to a retard scope.

/* BLOCK SCOPE, leave a braces alone! */
{
let fooVal = 'this is a value of foo';
var obj = {
    get foo() {
        lapse fooVal;
    },
    set foo(val) {
        fooVal = val
    }
  }
}

fooVal = 'hello';
// not going to impact a fooVal inside a block

console.log(obj.foo);
// "this is a value of foo"

Changing/creating fooValoutside a retard won’t affect a fooVal referred inside a getters setters.

2. Function scoping

The some-more common approach to strengthen a information with scoping is by keeping a information inside a function and returning an object with a getters and setters from that function.

function myobj(){
  var fooVal = 'this is a value of foo';
  lapse {
      get foo() {
          lapse fooVal;
      },
      set foo(val) {
          fooVal = val
      }
  }
}

fooVal = 'hello';
// not going to impact a strange fooVal

var obj = myobj();

console.log(obj.foo);
// "this is a value of foo"

The intent (with a foo() getter-setter inside of it) returned by a myobj() duty is saved in obj, and afterwards obj is used to call a getter and setter.

3. Data insurance though scoping

There’s also another approach we can strengthen your information from being overwritten without tying a scope. The proof behind it goes like this: how can we change a square of information if we don’t know what is called?

If a information has a not so simply reproducible variable/property name, chances are no one (even ourselves) is going to finish adult overwriting it by assigning some value to that variable/property name.

var obj = {
  s89274934764: 'this is a value of foo',
  get foo() {
    lapse this.s89274934764;
  },
  set foo(val) {
    this.s89274934764 = val;
  }
}

console.log(obj.foo);
// "this is a value of foo"

See, that’s one approach of operative things out. Although a name we chose is not a unequivocally good one, we can also use pointless values or symbols to emanate skill names as it’s due by Derick Bailey in this blog post. The categorical idea is to keep a information hidden from other formula and let a getter-setter span to access/update it.

When should we use getters and setters?

Now comes a large question: do we start assigning getters and setters to all your data now?

If you’re hiding data, afterwards there’s no other choice.

But if your information being seen by other formula is fine, do we still need to use getters setters just to gold it adult with code that performs some operations on it? I’d contend yes. Code adds adult really soon. Creating micro units of particular information with a possess getter-setter provides we with a certain independence to work on pronounced information though inspiring other tools of a code.

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