Using Javascript to assign a new key to an object by merging existing keys

Question

Using Javascript to assign a new key to an object by merging existing keys

I'm struggling to articulately explain my situation, so please excuse me if this has been addressed before.

I am seeking to specify an object in the following manner:

var foo = [
   {
      firstName : 'John',
      lastName : 'Doe',
      fullName : this.firstName + this.lastName
   },
    // OR
   {
      firstName : 'Jane',
      lastName : 'Doe',
      herID : Do-something with the first and last name that were just defined, such as computeCombination(firstName, lastName)
   }
]

Can this type of declaration be achieved?

I must finalize the declaration of foo immediately and I cannot make alterations to the object later on. Additionally, I wish to avoid using indexes here, like accessing elements via foo[0].firstName etc..

The primary reason for my request is that I want to eliminate repetitive strings, since they are verbose. Furthermore, each object in the array may require a different logic for the final key.

Thank you

javascript arrays object declaration key-value

Answer 1

Answer №1

One way to achieve this is by utilizing getter functions.

let person = [ 
   {
      firstName : 'Alice',
      lastName : 'Smith',
      get fullName(){ return this.firstName +' '+ this.lastName; }
   }]


console.log( person[0].fullName ); //Alice Smith

Check out this working example on JSFiddle

Answer 2

One way to achieve this is by utilizing getter functions.

let person = [ 
   {
      firstName : 'Alice',
      lastName : 'Smith',
      get fullName(){ return this.firstName +' '+ this.lastName; }
   }]


console.log( person[0].fullName ); //Alice Smith

Check out this working example on JSFiddle

Answer 3

Answer №2

It's not possible to achieve what you're asking for using a "static" declaration as shown in your code snippet. In a static declaration, the reference to this is not set to the object, making it impossible to access other properties of the object. However, if you want similar logic for creating the fullName property, you can use a dynamic declaration with a constructor like this:

function Person(firstName, lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
   this.fullName = firstName + " " + this.lastName;
}

var people = [new Person("John", "Doe"), new Person("Jane", "Doe")];

If you need different logic for each entry, you can pass a callback function into the Person() constructor to define the specific logic to use:

function Person(firstName, lastName, fn) {
   this.firstName = firstName;
   this.lastName = lastName;
   this.fullName = fn(firstName, lastName);
}

function combine(f, l) { return f + " " + l;}
function makeID(f, l) {return f.slice(0, 1) + l;}

var people = [new Person("John", "Doe", combine), new Person("Jane", "Doe", makeID)];

If you require different properties for each object in the array, consider using distinct constructors based on your needs. Here's an example with separate constructors:

function PersonName(firstName, lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
   this.fullName = firstName + " " + lastName;
}

function PersonID(firstName, lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
   this.herID = firstName.slice(0, 1) + lastName;
}

var people = [new PersonName("John", "Doe"), new PersonID("Jane", "Doe")];

There are various options available depending on your requirements.

Answer 4

It's not possible to achieve what you're asking for using a "static" declaration as shown in your code snippet. In a static declaration, the reference to this is not set to the object, making it impossible to access other properties of the object. However, if you want similar logic for creating the fullName property, you can use a dynamic declaration with a constructor like this:

function Person(firstName, lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
   this.fullName = firstName + " " + this.lastName;
}

var people = [new Person("John", "Doe"), new Person("Jane", "Doe")];

If you need different logic for each entry, you can pass a callback function into the Person() constructor to define the specific logic to use:

function Person(firstName, lastName, fn) {
   this.firstName = firstName;
   this.lastName = lastName;
   this.fullName = fn(firstName, lastName);
}

function combine(f, l) { return f + " " + l;}
function makeID(f, l) {return f.slice(0, 1) + l;}

var people = [new Person("John", "Doe", combine), new Person("Jane", "Doe", makeID)];

If you require different properties for each object in the array, consider using distinct constructors based on your needs. Here's an example with separate constructors:

function PersonName(firstName, lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
   this.fullName = firstName + " " + lastName;
}

function PersonID(firstName, lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
   this.herID = firstName.slice(0, 1) + lastName;
}

var people = [new PersonName("John", "Doe"), new PersonID("Jane", "Doe")];

There are various options available depending on your requirements.

Using Javascript to assign a new key to an object by merging existing keys

Answer №1

Answer №2

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