CODEWITHSUNDEEP
javascriptobject
hguser
hguser

Reputation: 36028

javascript constructor

Code:

1)

function Person(name,age){
  this.name=name;
  this.age=age;
}

var p=new Person('stack',100);
console.dir(p);
console.info(p.name);//'stack'.

But I wonder why I can create a new person use:

var p2=new Person(); //no error

There is not a constructor like:

function Person(){}

why?

2)

function Person(name,age){
  var _name,_age;
  this._name=name;
  this._age=age;
}

var p=new Person('stack',100);
console.dir(p);

What's the difference between this and the 1)'s manner?

Upvotes: -1

Views: 268

Answers (2)

stecb
stecb

Reputation: 14746

1) it's not mandatory to respect equals number of parameters a function can receive in Javascript. In that case (p2) they will be undefined.

2) you're declaring 2 'private' (just local) variables with var _name,_age; .. there's no need if you're not using them inside that scope.

Upvotes: 0

Felix Kling
Felix Kling

Reputation: 816404

If you don't pass parameters to a function, they will be undefined inside the function. You can pass any number of parameters to a function, you just need the name.

The only difference in the second version is that you define two local variables which you don't use and that you name the properties differently. Note that var _name is not the same as this._name.

Upvotes: 5

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