how to add a property to an object?

Question

Given an object that has a "firstName" property and a "lastName" property, "addFullNameProperty" returns a "fullName" property whose value is a string with the first name and last name separated by a space.

var person = {
  firstName: 'Jade',
  lastName: 'Smith'
};
addFullNameProperty(person);
console.log(person.fullName); // --> 'Jade Smith'

my code :

function addFullNameProperty(obj) {
  // your code here
  obj[fullName] = obj.firstName + obj.lastName;
}

Answer 1

Just simple set:

obj.fullName instead of  obj[fullName]

Or

obj['fullName']

Because fullName in your code is undefined variable. So JS alert error.

Answer 2

Either use obj.fullName or obj['fullName']

But a more correct solution would be

function addFullNameProperty(obj) {
  // your code here
  Object.defineProperty(obj, 'fullName', {
    get:  function(){
            return this.firstName + ' ' + this.lastName;
          }, 
    configurable:false
  });
}

var person = {
  firstName: 'Jade',
  lastName: 'Smith'
};

addFullNameProperty(person);

console.log(person.fullName); // --> 'Jade Smith'

person.firstName = "Mike";

console.log(person.fullName); // --> 'Mike Smith'

This way your object will always return the correct fullName.

Answer 3

If you want to add the space into the name, you will need to do string interpolation, like so:

`${obj.firstName} ${obj.lastName}`

and complement this with Gaby's answer about switching to dot notation, obj.fullName

Answer 4

Add new property to an existing object:

const person = {
  firstName: 'Jade',
  lastName: 'Smith'
};

person.fullName = `${person.firstName} ${person.lastName}`;

same as:

person['fullName'] = `${person.firstName} ${person.lastName}`;

or using method:

const person = {
    firstName: 'Jade',
    lastName: 'Smith',
    fullName(){ 
        return `${this.firstName} ${this.lastName}`;
    }
};

person.fullName(); // Jade Smith

You can also use defineProperty

Answer 5

Try this

return obj.fullName = obj.firstName + " " + obj.lastName