get keys of json-object in JavaScript

Question

I have a json-object in JavaScript and I want to get the used keys in it  My JavaScript-Code looks like this   var jsonData      person   me   age   30     person   you   age   25       And I want a loop that alerts me  person  and  age   which are the keys of the first object in the json-Array

User · Answer

The working code    x000D   x000D  var jsonData     person  me   age   30    person  you  age  25     x000D   x000D  for var obj in jsonData   x000D      if jsonData hasOwnProperty obj    x000D      for var prop in jsonData obj    x000D          if jsonData obj  hasOwnProperty prop    x000D             alert prop         jsonData obj  prop    x000D            x000D        x000D    x000D    x000D   x000D   x000D

User · Answer

What you have is just an object  not a  json-object   JSON is a textual notation  What you ve quoted is JavaScript code using an array initializer and an object initializer  aka   object literal syntax      If you can rely on having ECMAScript5 features available  you can use the Object keys function to get an array of the keys  property names  in an object  All modern browsers have Object keys  including IE9     Object keys jsonData  forEach function key        var value   jsonData key                      The rest of this answer was written in 2011  In today s world  A  You don t need to polyfill this unless you need to support IE8 or earlier      and B  If you did  you wouldn t do it with a one-off you wrote yourself or grabbed from an SO answer  and probably shouldn t have in 2011  either   You d use a curated polyfill  possibly from es5-shim or via a transpiler like Babel that can be configured to include polyfills  which may come from es5-shim    Here s the rest of the answer from 2011   Note that older browsers won t have it  If not  this is one of the ones you can supply yourself   if  typeof Object keys      function          function             var hasOwn   Object prototype hasOwnProperty          Object keys   Object keys          function Object keys obj                var keys       name              for  name in obj                    if  hasOwn call obj  name                         keys push name                                               return keys                          That uses a for  in loop  more info here  to loop through all of the property names the object has  and uses Object prototype hasOwnProperty to check that the property is owned directly by the object rather than being inherited    I could have done it without the self-executing function  but I prefer my functions to have names  and to be compatible with IE you can t use named function expressions  well  not without great care   So the self-executing function is there to avoid having the function declaration create a global symbol

User · Answer

var jsonData      person   me   age   30     person   you   age   25      for var i in jsonData       var key   i      var val   jsonData i       for var j in val           var sub key   j          var sub val   val j           console log sub key             EDIT  var jsonObj     person   me   age   30    Object keys jsonObj       returns   person    age     Object has a property keys  returns an Array of keys from that Object  Chrome  FF  amp  Safari supports Object keys

[javascript] get keys of json-object in JavaScript

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