Get the key of an object from within the object

Question

I have an object like this which is a collection of key=>function pairs.

 var hashes = {
    "a": function () {
        console.log($(this));
    return 'Fanta';
  },
  'b': function () {
        console.log($(this));
    return 'Pepsi';
  },
  'c': function () {
        console.log($(this));
    return 'Lemonade';
  }
};

hashes["a"]();
hashes["b"]();

I want to get the name of the key from within the function i.e. I was expecting console.log($(this)) to return "a" for 1st function, "b" for 2nd function and so on.. But since hashes is calling the function, it returns hashes object.

Is there any way to get key of the object from within the function (I need only corresponding key to the function being called)

@limelights: Do you mean like: hashes["a"]("a"); I can do it but I wanted to know if there is a way to do this without passing value. — Vignesh T.V.
– Vignesh T.V., Commented Sep 5, 2015 at 3:31
There is no way that I'm aware of. The function doesn't actually belong to the hashes object or to the individual key, rather that object property holds a reference to the function. You could have other references to the function that aren't part of the object, e.g., var x = hashes.a; x();. (returns 'Fanta') If you give the functions names to match the keys you could try arguments.callee.name, but that's deprecated and won't work in strict mode. — nnnnnn
– nnnnnn, Commented Sep 5, 2015 at 3:31
@nnnnnn: Thanks for your reply. I get you. But still, I will wait to see if there is any solution for this. I was using this as an alternative to switch case — Vignesh T.V.
– Vignesh T.V., Commented Sep 5, 2015 at 3:35

Tyler Eich · Accepted Answer · 2015-09-05 14:09:26Z

1

Here's one way to do it:

var hashes = {
  'a': 'Fanta',
  'b': 'Pepsi',
  'c': 'Lemonade'
};

var logger = function( key, value ) {
  console.log( key );
  return value;
};

for ( var key in hashes ) {
  if ( hashes.hasOwnProperty( key ) ) {
    var value = hashes[ key ];
    hashes[ key ] = logger.bind( null, key, value );
  }
}

hashes.a(); // "a"
hashes.b(); // "b"
hashes.c(); // "c"

Demo on JSBin

edited Sep 5, 2015 at 14:09

answered Sep 5, 2015 at 4:12

Tyler Eich

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2 Comments

Vignesh T.V. Over a year ago

Oh, wait.. I get your code now. Seems you are using 2 variables to achieve this.. But this will work...

Tyler Eich Over a year ago

Updated the code to use one hashes variable instead of two. Also removed dependency on lexical this.

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