有没有办法将 firstName 和 lastName 的第一个字母大写并使其成为 Javascript 中的首字母

Question

// Add a method to the Person's prototype called "getInitials" that returns the first letter of their first and last name, both capitalized.

 function Person(firstName, lastName) { Person.prototype.getInitials = function() { let name = (firstName, lastName) => { return name.split(' ').map(word => word.substr(0, 1).toUpperCase() + word.substr(1, word.length)).join(' '); }; } } /* Do not modify code below this line */ const johnDoe = new Person('john', 'doe'); console.log(johnDoe.getInitials(), '<-- should be "JD"');

Answer 1

1. Do not set the prototype inside Person 's constructor

Every time you instantiate a Person you will modify the prototype of Person which is not what you want to do. Set it once (outside of Person ) is enough.

2. You don't need to substring everything, just keep the first letter

 function Person(firstName, lastName) { this.firstName = firstName; this.lastName = lastName; } Person.prototype.getInitials = function() { return `"${(this.firstName[0]+this.lastName[0]).toUpperCase()}"`; } /* Do not modify code below this line */ const johnDoe = new Person('john', 'doe'); console.log(johnDoe.getInitials(), '<-- should be "JD"');

Answer 2

Can't it be like this below, isn't it easier?

You don't need to define prototype inside the Person , but can use this . Also you can just get the first character by index position [0] , without splits or substrings.

 function Person(firstName, lastName) { this.getInitials = function() { return firstName[0].toUpperCase() + lastName[0].toUpperCase() }; } const johnDoe = new Person('john', 'doe'); console.log(johnDoe.getInitials()); const maryAnn = new Person('mary', 'ann'); console.log(maryAnn.getInitials());

Of course, I would recommend some verification to see if firstName and lastName aren't null/undefined before get its first character.

If you want to define prototype, then do it outside of Person

function Person(f,n){...};
Person.prototype.getInitials = function(){...}

Answer 3

 var firstName ="jhon"; var lastName = "doe"; getInitials= function(fname,lname){ return fname[0].toUpperCase()+' '+lname[0].toUpperCase(); } console.log(getInitials(firstName,lastName));

Answer 4

YOu can do something like using classes

 class Person { constructor (firstName, lastName) { this.firstName = firstName; this.lastName = lastName; } getInitials () { return this.firstName[0].toUpperCase() + this.lastName[0].toUpperCase(); } } const person = new Person('jon', 'doe'); console.log(person.getInitials());

Answer 5

Answer:

To do what you're trying to do we can hardcode getInitials as a method on our Person Constructor:

// Construct Object
function Person(firstName, lastName) {
  return Object.assign(this, { firstName, lastName });
}

// adjust Constructor Prototype
Person.prototype.getInitials = function() {
         return `${this.firstName[0]} ${this.lastName[0]}`.toUpperCase();
}

 // Construct Object function Person(firstName, lastName) { return Object.assign(this, { firstName, lastName }); } // adjust Constructor Prototype Person.prototype.getInitials = function() { return `${this.firstName[0]} ${this.lastName[0]}`.toUpperCase(); } /* Do not modify code below this line */ const johnDoe = new Person('john', 'doe'); console.log( johnDoe.getInitials() )

---

Alternatives:

In cases like this it's often beneficial to keep in line the idea that methods are actions instead of property seeking .

For instance, instead of equipping your constructed Object with something like Person.getInitials it would make more sense, logically, to be able to simply write Person.initials .

In keeping with that we can choose to hardcode the property:

function Person(firstName, lastName) {
  return Object.assign(this, {
    firstName,
    lastName,
    initials: `${firstName[0]} ${lastName[0]}`.toUpperCase()
  })
}

 function Person(firstName, lastName) { return Object.assign(this, { firstName, lastName, initials: `${firstName[0]} ${lastName[0]}`.toUpperCase() }) } /* Do not modify code below this line */ const johnDoe = new Person('john', 'doe'); console.log(johnDoe.initials)

Or, if we're looking to be more clear with our code ( always a good thing ), we could do the following utilizing an accessor property ( otherwise known as getters and/or setters ):

function Person(firstName, lastName) {

  // define properties
  Object.defineProperties(this, {
    firstName: {
      value: firstName
    },
    lastName: {
      value: lastName
    },
    initials: {
      get: function() {
        return `${firstName[0]} ${lastName[0]}`.toUpperCase();
      }
    }
  });

}

 function Person(firstName, lastName) { // define properties Object.defineProperties(this, { firstName: { value: firstName }, lastName: { value: lastName }, initials: { get: function() { return `${firstName[0]} ${lastName[0]}`.toUpperCase(); } } }); } /* Do not modify code below this line */ const johnDoe = new Person('john', 'doe'); console.log( johnDoe.initials )

---

Aside:

An additional benefit of not extending the prototype unnecessarily is that you are able to prevent changes to these Constructed Objects by freezing them when they are created. This adds some peace-of-mind if, in the future, some other Developer tries to alter the Object on the fly instead of altering the Constructor properly. This also doubles as a, albeit flimsy, piece of extra security for your code.

function Person(firstName, lastName) {

  // define properties
  Object.defineProperties(this, {
    firstName: {
      value: firstName
    },
    lastName: {
      value: lastName
    },
    initials: {
      get: function() {
        return `${firstName[0]} ${lastName[0]}`.toUpperCase();
      }
    }
  });

  // prevent alteration
  Object.freeze(this);

}

 function Person(firstName, lastName) { // define properties Object.defineProperties(this, { firstName: { value: firstName }, lastName: { value: lastName }, initials: { get: function() { return `${firstName[0]} ${lastName[0]}`.toUpperCase(); } } }); // prevent alteration Object.freeze(this); } /* Do not modify code below this line */ const johnDoe = new Person('john', 'doe'); console.log(johnDoe.initials) console.log("Attempting to change firstName to Zak..."); johnDoe.firstName = "Zak"; console.log("But firstName remains: " + johnDoe.firstName);

---

Conclusion:

Though ultimately everything is entirely open to your circumstances and discretion, I hope this answer helps illuminate some of the different options you have to produce clearer and more efficient code!

Happy Coding!