Get array of object s keys

Question

I would like to get the keys of a JavaScript object as an array  either in jQuery or pure JavaScript   Is there a less verbose way than this   var foo      alpha     puffin    beta     beagle     var keys       for  var key in foo        keys push key

User · Answer

If you decide to use Underscore js you better do  var foo      alpha     puffin    beta     beagle     var keys         each  foo  function  val  key         keys push key       console log keys

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In case you re here looking for something to list the keys of an n-depth nested object as a flat array    x000D   x000D  const getObjectKeys    obj  prefix         gt    x000D    return Object entries obj  reduce  collector   key  val     gt    x000D      const newKeys        collector  prefix      prefix    key     key   x000D      if  Object prototype toString call val        object Object      x000D        const newPrefix   prefix      prefix    key     key x000D        const otherKeys   getObjectKeys val  newPrefix  x000D        return      newKeys     otherKeys   x000D        x000D      return newKeys x000D           x000D    x000D   x000D  console log getObjectKeys  a  1  b  2  c    d  3  e    f  4       x000D   x000D   x000D

User · Answer

I don t know about less verbose but I was inspired to coerce the following onto one line by the one-liner request  don t know how Pythonic it is though     var keys    function o  var ks     for var k in o  ks push k   return ks   foo

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Summary  For getting all of the keys of an Object you can use Object keys    Object keys   takes an object as an argument and returns an array of all the keys   Example    x000D   x000D  const object     x000D    a   string1   x000D    b  42  x000D    c  34 x000D     x000D   x000D  const keys   Object keys object  x000D   x000D  console log keys   x000D   x000D  console log keys length     we can easily access the total amount of properties the object has x000D   x000D   x000D    In the above example we store an array of keys in the keys const  We then can easily access the amount of properties on the object by checking the length of the keys array   Getting the values with  Object values    The complementary function of Object keys   is Object values    This function takes an object as an argument and returns an array of values  For example    x000D   x000D  const object     x000D    a   random   x000D    b  22  x000D    c  true x000D     x000D   x000D   x000D  console log Object values object    x000D   x000D   x000D

User · Answer

You can use jQuery s   map   var foo      alpha     puffin    beta     beagle     keys     map foo  function v  i     return i

User · Answer

Of course  Object keys   is the best way to get an Object s keys  If it s not available in your environment  it can be trivially shimmed using code such as in your example  except you d need to take into account your loop will iterate over all properties up the prototype chain  unlike Object keys   s behaviour    However  your example code     var foo      alpha     puffin    beta     beagle     var keys       for  var key in foo        keys push key       jsFiddle      could be modified  You can do the assignment right in the variable part   var foo      alpha     puffin    beta     beagle     var keys       i   0  for  keys i    in foo       jsFiddle   Of course  this behaviour is different to what Object keys   actually does  jsFiddle   You could simply use the shim on the MDN documentation

User · Answer

Use Object keys    x000D   x000D  var foo     x000D     alpha    puffin   x000D     beta    beagle  x000D     x000D   x000D  var keys   Object keys foo   x000D  console log keys       alpha    beta    x000D      or maybe some other order  keys are unordered   x000D   x000D   x000D    This is an ES5 feature  This means it works in all modern browsers but will not work in legacy browsers    The ES5-shim has a implementation of Object keys you can steal

[javascript] Get array of object's keys

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