Use Object method in anthor object without using new keyword in javascript

Question

I have two constructor function, I just want to use object a method in object b without using new keyword because I dont want to create an object with all its properties when there is no need. for example, inside constructor b I want to use constructor b method.

function a(){
  this.first=function(){
    return 'aaaaaa'
  }
  this.last=function (){
    return 'bbbbb'
  }
}

function b(){
  this.name= //call method last of constructor a.
}    

var person= new b();
console.log(person.name) //bbbbb

Note: Constructor a contains two method. So In given example I do not have any use of method first but may required later on. So I don't want to create new a(). I just want to call it directly

You can't do that. Move the methods to the prototype.

SLaks
– SLaks

2014-12-04 19:01:42 +00:00
Commented Dec 4, 2014 at 19:01 — SLaks
– SLaks, Commented Dec 4, 2014 at 19:01

juvian · Accepted Answer · 2014-12-04 19:03:07Z

2

function a(){

}

a.prototype.last=function(){
    return 'bbbb'
}

function b(){
    this.name= a.prototype.last()//call method last of constructor a.
}    

var person= new b();
console.log(person.name) //bbbbb

answered Dec 4, 2014 at 19:03

juvian

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2 Comments

Jitender Over a year ago

Your is working well. Just for knowledge what is the difference between assigning a method directly in constructor and adding method using prototype

juvian Over a year ago

Well, here is a good detailed answer : stackoverflow.com/questions/2784844/…

Laxmikant Dange · Accepted Answer · 2014-12-05 08:16:33Z

1

There are various ways to get its function.

create name space

var a={
  first:function(){
    return 'aaaaaa'
  },
  last:function (){
    return 'bbbbb'
  }
}


function b(){
  this.name= a.last()
}

Add methods to prototype property

var a=function(){
};
a.prototype.first=function(){
   return 'aaaaaa'
};
a.prototype.last=function (){
    return 'bbbbb'
}
function b(){
  this.name= a.prototype.last()
}

finally this will be same as previous one.

call a() and call its methods directly.(without a())

Third is call a() which will create "first" & "last" methods which will be function for its context. and then call your method. But this way is not recommended. for ex.

function a(){
    this.first=function(){
        return 'aaaaaa'
    }
    this.last=function (){
        return 'bbbbb'
   }
}
a()
function b(){   this.name= last()}    

var person= new b(); console.log(person.name) //bbbbb}}

edited Dec 5, 2014 at 8:16

answered Dec 4, 2014 at 19:11

Laxmikant Dange

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3 Comments

Jitender Over a year ago

Your first example is not working. When I have removed this. then it is working fine. I Just want to know about your 3 point where you said "call a() and call its methods directly.(without a())", Can you put some example of that

Laxmikant Dange Over a year ago

@amit, I made changes to answer, please refer it.

Laxmikant Dange Over a year ago

sorry there is no need of this in namespace. sorry for my typo mistake

Ceres · Accepted Answer · 2014-12-04 19:01:54Z

1

function a(){

  this.first=function(){
    return 'aaaaaa';
  }

  this.last= lastfunc;

}

function b(){
  this.name= lastFunct()
}

var person= new b();
console.log(person.name) //bbbbb

function lastFunct() {
  return 'bbbbb';
}

answered Dec 4, 2014 at 19:01

Ceres

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3 Comments

Patrick Over a year ago

I know that you are replicating OP answer as close as possible, but might be better to add these functions to the constructor prototype. e.g. b.prototype.name = function..., a.prototype.last = lastfunc, a.prototype.first = function...

Ceres Over a year ago

@Patrick I agree, but I'll leave it as is since there is another answere with that solution. It's still valid.

Patrick Over a year ago

Agreed. I provided the comment before the other answer :)

Felix Kling · Accepted Answer · 2014-12-04 19:01:51Z

0

first and last don't exist until you create an instance of a. If those are just static methods, why not use an object?

var a = {
  first: function(){
    return 'aaaaaa'
  },
  last: function (){
    return 'bbbbb'
  }
};

answered Dec 4, 2014 at 19:01

Felix Kling

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