I'm used to a javascript object constructors looking like this
function person(first, last) {
this.firstName = first;
this.lastName = last;
}
var dude = new person("the", "dude");
But sometimes I see the constructor return "this", like so
function person(first, last) {
this.firstName = first;
this.lastName = last;
return this;
}
What's up with returning this at the end?
There's no point in returning this from a constructor, but you are allowed to return any object you'd like. If no object is explicitly returned, this is implicitly returned.
A possible use case is:
function person(first, last) {
if(!(this instanceof person)) {
return new person(first, last);
}
this.first = first;
this.last = last;
}
var person1 = new person('first', 'person');
var person2 = person('second', 'person'); // <- without "new"
console.log(person1, person2);
new" problem for anyone that wants further explanation as to what's going on with this question.The only case that I know it could mean something is if you instantiate your objects in the following manner;
person.call(Object.create(person.prototype), 'Jack', 'Brown');
The above example requires that you return this;
What can be done, but should be avoided, is to return a different object than this
function person(first, last) {
return {first: first, last: last};
}
(new Person() ) instanceof Person // false
this is returned so the caller can chain calls together.
console.log(new person('First', 'Last').firstName);
