Getting a list of associative array keys

Question

I have an associative array in JavaScript  var dictionary          quot cats quot    1 2 3 4 5        quot dogs quot    6 7 8 9 10      How do I get this dictionary s keys  I e   I want var keys     quot cats quot    quot dogs quot      Just to get the terminology correct - there is no such thing as an  associative array  in JavaScript - this is technically just an object and it is the object keys we want

User · Answer

for  var key in dictionary         Do something with key    It s the for  in statement

User · Answer

Just a quick note  Be wary of using for  in if you use a library  jQuery  Prototype  etc    as most of them add methods to created Objects  including dictionaries   This will mean that when you loop over them  method names will appear as keys  If you are using a library  look at the documentation and look for an enumerable section  where you will find the right methods for iteration of your objects

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I am currently using Rob de la Cruz s reply  Object keys obj   And in a file loaded early on I have some lines of code borrowed from elsewhere on the Internet which cover the case of old versions of script interpreters that do not have Object keys built in  if   Object keys        Object keys   function object            var keys               for  var o in object                if  object hasOwnProperty o                     keys push o                                   return keys            I think this is the best of both worlds for large projects  simple modern code and backwards compatible support for old versions of browsers  etc  Effectively it puts JW s solution into the function when Rob de la Cruz s Object keys obj  is not natively available

User · Answer

Simple jQuery way  This is what I use  DictionaryObj being the JavaScript dictionary object you want to go through  And value  key of course being the names of them in the dictionary    each DictionaryObj  function  key  value           quot  storeDuplicationList quot            append    quot  lt li gt  lt  li gt  quot            attr  quot value quot   key           text value

User · Answer

Try this   var keys       for  var key in dictionary      if  dictionary hasOwnProperty key         keys push key           hasOwnProperty is needed because it s possible to insert keys into the prototype object of dictionary  But you typically don t want those keys included in your list   For example  if you do this   Object prototype c   3  var dictionary    a  1  b  2     and then do a for   in loop over dictionary  you ll get a and b  but you ll also get c

User · Answer

You can use  Object keys obj  Example   x000D   x000D  var dictionary        cats    1  2  37  38  40  32  33  35  39  36      dogs    4  5  6  3  2         Get the keys var keys   Object keys dictionary    console log keys   x000D   x000D   x000D   See reference below for browser support  It is supported in Firefox 4 20  Chrome 5  and Internet  Explorer  9  Object keys   contains a code snippet that you can add if Object keys   is not supported in your browser

[javascript] Getting a list of associative array keys

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