Why my own "toString()" function doesn't work in my javascript?

Question

I tried in my chrome debug console:

>function m(){function toString(){return "abc"}}
undefined
>new m().toString()
"[object Object]"

I expect it to print "abc". Why?

A function used as a constructor should return an object. If it doesn't, the return value is ignored and an object is returned instead. — Teemu
– Teemu, Commented Sep 1, 2016 at 7:37
You need to learn the difference between local variables and object properties. — Barmar
– Barmar, Commented Sep 1, 2016 at 7:39

Nina Scholz · Accepted Answer · 2016-09-01 07:42:40Z

4

You are not using your own toString method (which is a private function inside of m), but the one from Object.

For your own method, you need to assign your toString method to m's prototype, like

m.prototype.toString = function () { return 'abc'; };

function m() {}
m.prototype.toString = function () { return 'abc'; };

console.log((new m).toString());

answered Sep 1, 2016 at 7:36

Nina Scholz

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Comments

giraysam · Accepted Answer · 2016-09-01 07:45:57Z

2

try this.

function m() {
  this.toString = function() {
    return "abc";
  }
}

var m1 = new m();
alert(m1.toString());

answered Sep 1, 2016 at 7:45

giraysam

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Kabir Hossain · Accepted Answer · 2016-09-01 07:48:02Z

0

Your code is wrong. You can try this code and check output here http://jsbin.com/luremulano/edit?html,js,console,output

  console.log(m('abc'));

  function m(a){
      return a.toString();  
  }

answered Sep 1, 2016 at 7:48

Kabir Hossain

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