How to access the first property of a Javascript object

Question

Is there an elegant way to access the first property of an object      where you don t know the name of your properties without using a loop like for    in or jQuery s   each   For example  I need to access foo1 object without knowing the name of foo1   var example         foo1       stuff1          foo2       stuff2          foo3       stuff3

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The top answer could generate the whole array and then capture from the list  Here is an another effective shortcut  var obj     first   someVal     Object entries obj  0  1     someVal

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Use Object keys to get an array of the properties on an object  Example   var example         foo1       stuff1          foo2       stuff2          foo3       stuff3         var keys   Object keys example        gt    foo1    foo2    foo3    Note  the order here is not reliable    Documentation and cross-browser shim provided here  An example of its use can be found in another one of my answers here   Edit  for clarity  I just want to echo what was correctly stated in other answers  the key order in javascript objects is undefined

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I don t recommend you to use Object keys since its not supported in old IE versions  But if you really need that  you could use the code above to guarantee the back compatibility   if   Object keys    Object keys    function      var hasOwnProperty   Object prototype hasOwnProperty      hasDontEnumBug      toString  null   propertyIsEnumerable  toString        dontEnums            toString          toLocaleString          valueOf          hasOwnProperty          isPrototypeOf          propertyIsEnumerable          constructor             dontEnumsLength   dontEnums length   return function  obj      if  typeof obj      object   amp  amp  typeof obj      function     obj     null  throw new TypeError  Object keys called on non-object       var result          for  var prop in obj        if  hasOwnProperty call obj  prop   result push prop          if  hasDontEnumBug        for  var i 0  i  lt  dontEnumsLength  i            if  hasOwnProperty call obj  dontEnums i    result push dontEnums i                return result            Feature     Firefox  Gecko 4  2 0    Chrome 5  Internet Explorer 9  Opera 12    Safari 5  More info  https   developer mozilla org en-US docs JavaScript Reference Global Objects Object keys  But if you only need the first one  we could arrange a shorter solution like   var data     key1   123   key2   456    var first       for key in data       if data hasOwnProperty key            first key   key          first content    data key           break          console log first       key  key  content  123

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Here is a cleaner way of getting the first key   x000D   x000D  var object         foo1   value of the first property  foo1        foo2       stuff2          foo3       stuff3         let  firstKey    Object keys object   console log firstKey  console log object firstKey   x000D   x000D   x000D

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we can also do with this approch   var example       foo1       stuff1        foo2       stuff2        foo3       stuff3         Object entries example  0  1

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You can also do Object values example  0

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You can use Object prototype keys which returns all the keys of an object in the same order  So if you want the first object just get that array and use the first element as desired key   const o      key1    value1    key2    value2    const idx   0     add the index for which you want value var key   Object keys o  idx   value   o key  console log key value      key2 value2

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To get the first key name in the object you can use   var obj     first   someVal     Object keys obj  0     returns  first    Returns a string  so you cant access nested objects if there were  like   var obj     first    someVal     id   1     Here with that solution you can t access id   The best solution if you want to get the actual object is using lodash like   obj   first   keys obj    id   To return the value of the first key   if you don t know exactly the first key name    var obj     first   someVal     obj Object keys obj  0      returns  someVal    if you know the key name just use   obj first   or  obj  first

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If you need to access  the first property of an object   it might mean that there is something wrong with your logic  The order of an object s properties should not matter

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Solution with lodash library     find example       gt   name   foo1     but there is no guarantee of the object properties internal storage order because it depends on javascript VM implementation

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Try the for     in loop and break after the first iteration   for  var prop in object           object prop      break

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if someone prefers array destructuring const  firstKey    Object keys object

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Any reason not to do this    gt  example map x   gt  x name     3    foo1    foo2    foo3

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Use an array instead of an object  square brackets    var example         stuff1           stuff2           stuff3       var fist   example 0     Note that you lose the  foo  identifiers  But you could add a name property to the contained objects   var example         name   foo1      stuff1         name   foo2      stuff2         name   foo3      stuff3        var whatWasFirst   example 0  name

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A one-rule version   var val   example function     for  var k in example  return k

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There isn t a  first  property  Object keys are unordered   If you loop over them with for  var foo in bar  you will get them in some order  but it may change in future  especially if you add or remove other keys

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var obj     first   someVal     obj Object keys obj  0      returns  someVal    Using this you can access also other properties by indexes  Be aware tho  Object keys return order is not guaranteed as per ECMAScript however unofficially it is by all major browsers implementations  please read https   stackoverflow com a 23202095 for details on this

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No  An object literal  as defined by MDC is      a list of zero or more pairs of property names and associated values of an object  enclosed in curly braces         Therefore an object literal is not an array  and you can only access the properties using their explicit name or a for loop using the in keyword

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This has been covered here before   The concept of first does not apply to object properties  and the order of a for   in loop is not guaranteed by the specs  however in practice  it is reliably FIFO except critically for chrome  bug report   Make your decisions accordingly

[javascript] How to access the first property of a Javascript object?

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