Question

I’m learning javascript and was going through an example here:
https://developer.mozilla.org/en/A_re-introduction_to_JavaScript

function personFullName() {  
    return this.first + ' ' + this.last;  
}  
function personFullNameReversed() {  
    return this.last + ', ' + this.first;  
}  
function Person(first, last) {  
    this.first = first;  
    this.last = last;  
    this.fullName = personFullName;  
    this.fullNameReversed = personFullNameReversed;  
}  
var x = new Person('mickey', 'mouse');
document.write(x.fullName());

Why are the lines of code

    this.fullName = personFullName;  
    this.fullNameReversed = personFullNameReversed;  

instead of

    this.fullName = personFullName();  
    this.fullNameReversed = personFullNameReversed();  

I thought we’re setting this.fullName based on the return value of personFullName()

Answer 1

That code is making the “fullName” and “fullNameReversed” properties be functions, not simple properties.

Thus when you want the full name you’d write x.fullName();

Functions are objects in JavaScript and can be the value of variables and properties. This is a feature that makes JavaScript surprisingly powerful.