How do I access properties of a javascript object if I don t know the names

Question

Say you have a javascript object like this   var data     foo   bar   baz   quux       You can access the properties by the property name   var foo   data foo  var baz   data  baz      But is it possible to get these values if you don t know the name of the properties  Does the unordered nature of these properties make it impossible to tell them apart   In my case I m thinking specifically of a situation where a function needs to accept a series of name-value pairs  but the names of the properties may change   My thoughts on how to do this so far is to pass the names of the properties to the function along with the data  but this feels like a hack  I would prefer to do this with introspection if possible

User · Accepted Answer

Old versions of JavaScript   lt  ES5  require using a for  in loop   for  var key in data      if  data hasOwnProperty key            do something with key         ES5 introduces Object keys and Array forEach which makes this a little easier   var data     foo   bar   baz   quux      Object keys data        foo    baz   Object keys data  map function key   return data key          bar    quux   Object keys data  forEach function  key         do something with data key        ES2017 introduces Object values and Object entries   Object values data       bar    quux   Object entries data        foo    bar      baz    quux

User · Answer

var attr  object information      for attr in object            Get names and values of propertys with style  name   value        object information    attr           object attr      n            alert object information     Show all Object

User · Answer

You can use Object keys     which returns an array of a given object s own enumerable property names  in the same order as we get with a normal loop    You can use any object in place of stats    x000D   x000D  var stats     x000D    a  3  x000D    b  6  x000D    d  7  x000D    erijgolekngo  35 x000D    x000D      this is the answer here     x000D  for  var key in Object keys stats     x000D    var t   Object keys stats  key   x000D    console log t     value        stats t    x000D    x000D   x000D   x000D

User · Answer

You often will want to examine the particular properties of an instance of an object  without all of it s shared prototype methods and properties    Obj prototype toString  function            var A              for var p in this               if this hasOwnProperty p                    A A length   p     this p                                return A join

User · Answer

for var property in data        alert property

User · Answer

function getDetailedObject inputObject        var detailedObject       properties       do           properties   Object getOwnPropertyNames  inputObject            for  var o in properties                detailedObject properties o     inputObject properties o                    while   inputObject   Object getPrototypeOf  inputObject           return detailedObject      This will get all properties and their values  inherited or own  enumerable or not  in a new object  original object is untouched  Now new object can be traversed using  var obj      b    4       example object var detailedObject   getDetailedObject obj   for var o in detailedObject        console log  key      o       value      detailedObject o

User · Answer

var obj      a   1  3  4    b  2   c    hi    there      for let r in obj      for in loop iterates all properties in an object  console log r       print all properties in sequence  console log obj r     print all properties values

User · Answer

You can loop through keys like this   for  var key in data      console log key       This logs  Name  and  Value    If you have a more complex object type  not just a plain hash-like object  as in the original question   you ll want to only loop through keys that belong to the object itself  as opposed to keys on the object s prototype   for  var key in data      if  data hasOwnProperty key         console log key           As you noted  keys are not guaranteed to be in any particular order  Note how this differs from the following   for each  var value in data      console log value       This example loops through values  so it would log Property Name and 0  N B   The for each syntax is mostly only supported in Firefox  but not in other browsers   If your target browsers support ES5  or your site includes es5-shim js  recommended   you can also use Object keys   var data     Name   Property Name   Value   0     console log Object keys data         gt    Name    Value     and loop with Array prototype forEach   Object keys data  forEach function  key      console log data key             gt  Logs  Property Name   0

[javascript] How do I access properties of a javascript object if I don't know the names?

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