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JavaScript Initials of name in Uppercase (I kept getting undefined)


// 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 = "first last";

let initials = Array.prototype.map.call(name.split(" "), function(x){ return x.substring(0,1).toUpperCase();}).join('');



/* Do not modify code below this line */

const johnDoe = new Person('john', 'doe');

console.log(johnDoe.getInitials(), '<-- should be "JD"');
Last edited by a moderator:
In JavaScript, there is a function called charAt() which you can use to get the letter at position 0. Like so:
Person.prototype.getInitials = function(){
    var first = this.firstName.charAt(0);
    var last = this.lastName.charAt(0);
    return first + last;

You can also use .toUpperCase() in case you want the initials to be capitalized.

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