使用相等运算符的Javascript函数和对象

Question

I am trying to understand Javascript concepts from https://developer.mozilla.org/en-US/docs/JavaScript/A_re-introduction_to_JavaScript . Please see the code below;

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;
}

I am confused why function personFullName() is called like

this.fullName = personFullName;

why it is not called like;

this.fullName = personFullName();

And same for the below;

this.fullNameReversed = personFullNameReversed;

I know functions are objects in javascript but i am unable to understand this concept?

Answer 1

Because the Person object is assigning itself a method , not the results of a function. That is the reason it doesn't call the function .

This way you can do this.

var p = new Person("Matt", "M");
p.fullName(); // Returns "Matt M"
p.fullNameReversed(); // Returns "M, Matt"