Getting the first index of an object

Question

Consider   var object       foo        bar        baz         How would I do this   var first   object 0   console log first     Obviously  that doesn   t work because the first index is named foo   not 0   console log object  foo       works  but I don   t know it   s named foo  It could be named anything  I just want the first

User · Answer

for first key of object you can use   console log Object keys object  0     print key s name   for value  console log object Object keys object  0      print key s value

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If you want something concise try   for  first in obj  break   alert first     wrapped as a function   function first obj        for  var a in obj  return a

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There is no way to get the first element  seeing as  hashes   objects  in JavaScript have unordered properties  Your best bet is to store the keys in an array   var keys     foo    bar    baz      Then use that to get the proper value   object keys 0

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You could do something like this   var object         foo  a  first        bar         baz        function getAttributeByIndex obj  index     var i   0    for  var attr in obj       if  index     i         return obj attr             i          return null      var first   getAttributeByIndex object  0      returns the value of the                                                first  0 index  attribute                                                of the object    a  first

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they re not really ordered  but you can do   var first  for  var i in obj        if  obj hasOwnProperty i   amp  amp  typeof i       function             first   obj i           break            the  hasOwnProperty   is important to ignore prototyped objects

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Based on CMS answer  I don t get the value directly  instead I take the key at its index and use this to get the value   Object keyAt   function obj  index        var i   0      for  var key in obj            if   index    0      i    return key             var obj         foo   1st       bar   2nd       baz   3rd      var key   Object keyAt obj  1   var val   obj key    console log key        gt   bar  console log val        gt   2nd

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Just for fun this works in JS 1 8 5  var obj    a  1  b  2  c  3   Object keys obj  0       a    This matches the same order that you would see doing  for  o in obj

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My solution   Object prototype   index   function index        var i   -1      for  var key in this                if  this hasOwnProperty key   amp  amp  typeof this key      function                 i          if  i  gt   index              return this key             return null    aObj     jack  3   peter  4   5   col    kk  function   alert  hell       till   ding    alert aObj   index 4

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Using underscore you can use   pairs to get the first object entry as a key value pair as follows     pairs obj  0    Then the key would be available with a further  0  subscript  the value with  1

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I had the same problem yesterday  I solved it like this   var obj             foo             bar             baz              first   null     key   null  for  var key in obj        first   obj key       if typeof first       function             break             first is the first enumerated property  and key it s corresponding key    Not the most elegant solution  and I am pretty sure that it may yield different results in different browsers  i e  the specs says that enumeration is not required to enumerate the properties in the same order as they were defined   However  I only had a single property in my object so that was a non-issue  I just needed the first key

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If the order of the objects is significant  you should revise your JSON schema to store the objects in an array           name   foo               name   bar               name   baz            or maybe           foo              bar              baz           As Ben Alpert points out  properties of Javascript objects are unordered  and your code is broken if you expect them to enumerate in the same order that they are specified in the object literal   there is no  first  property

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To get the first key of your object  const myObject         foo1     name   myNam1         foo2     name   myNam2       const result   Object keys myObject  0       result will return  foo1

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ES6  const  first    Object keys obj

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This will not give you the first one as javascript objects are unordered  however this is fine in some cases   myObject Object keys myObject  0

[javascript] Getting the first index of an object

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