How to find keys of a hash

Question

I know in javascript Objects double as hashes but i have been unable to find a built in function to get the keys   var h    a  b  c  d      I want something like   var k   h keys        k     a   c      It is simple to write a function myself to iterate over the items and add the keys to an array that I return  but is there a standard cleaner way to do that   I keep feeling it must be a simple built in function that I missed but I can t find it

User · Answer

I believe you can loop through the properties of the object using for in  so you could do something like this   function getKeys h      Array keys   new Array      for  var key in h      keys push key     return keys

User · Answer

if you are trying to get the elements only but not the functions then this code can help you  this getKeys   function      var keys   new Array    for var key in this         if  typeof this key       function              keys push key           return keys       this is part of my implementation of the HashMap and I only want the keys  this is the hashmap object that contains the keys

User · Answer

There is function in modern JavaScript  ECMAScript 5  called Object keys performing this operation   var obj      a    1   b    2   c    3   alert Object keys obj       will output   a    b    c     Compatibility details can be found here    On the Mozilla site there is also a snippet for backward compatibility   if  Object keys  Object keys   function o      if  o     Object o         throw new TypeError  Object keys called on non-object       var ret    p     for p in o  if Object prototype hasOwnProperty call o p   ret push p      return ret

User · Answer

This is the best you can do  as far as I know     var keys       for  var k in h keys push k

User · Answer

You could use Underscore js  which is a Javascript utility library     keys  one   1  two   2  three   3          gt    one    two    three

User · Answer

using jQuery you can get the keys like this   var bobject     primary  red  bg  maroon  hilite  green    var keys         each bobject  function key val   keys push key       console log keys        primary    bg    hilite     Or   var bobject     primary  red  bg  maroon  hilite  green      map bobject  function v k  return k       thanks to  pimlottc

User · Answer

you can use Object keys  Object keys h

User · Answer

For production code requiring a large compatibility with client browsers I still suggest Ivan Nevostruev s answer above with shim to ensure Object keys in older browsers  However  it s possible to get the exact functionality requested using ECMA s new defineProperty feature   As of ECMAScript 5 - Object defineProperty  As of ECMA5 you can use Object defineProperty   to define non-enumerable properties  The current compatibility still has much to be desired  but this should eventually become usable in all browsers   Specifically note the current incompatibility with IE8    Object defineProperty Object prototype   keys       value  function keys         var keys           for var i in this  if  this hasOwnProperty i           keys push i             return keys         enumerable  false      var o          a   1       b   2    for  var k in o        console log k  o k      console log o keys       OUTPUT    gt  a 1    gt  b 2    gt    a    b     However  since ECMA5 already added Object keys you might as well use   Object defineProperty Object prototype   keys       value  function keys         return Object keys this          enumerable  false       Original answer  Object prototype keys   function        var keys         for var i in this  if  this hasOwnProperty i           keys push i         return keys        Edit  Since this answer has been around for a while I ll leave the above untouched  Anyone reading this should also read Ivan Nevostruev s answer below   There s no way of making prototype functions non-enumerable which leads to them always turning up in for-in loops that don t use hasOwnProperty  I still think this answer would be ideal if extending the prototype of Object wasn t so messy

User · Answer

I wanted to use the top rated answer above  Object prototype keys   function          However when using in conjunction with the google maps API v3  google maps is non-functional   for  var key in h        works well

[javascript] How to find keys of a hash?

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