JavaScript object access variable property by name as string

Question

If I have a javascript object that looks like below  var columns       left  true    center   false    right   false     and I have a function that is passed both the object  and a property name like so    should return false var side   read prop columns   right      what would the body of read prop object  property  look like

User · Answer

Since I was helped with my project by the answer above (I asked a duplicate question and was referred here), I am submitting an answer (my test code) for bracket notation when nesting within the var:

_x000D_

<html>_x000D_
<head>_x000D_
  <script type="text/javascript">_x000D_
    function displayFile(whatOption, whatColor) {_x000D_
      var Test01 = {_x000D_
        rectangle: {_x000D_
          red: "RectangleRedFile",_x000D_
          blue: "RectangleBlueFile"_x000D_
        },_x000D_
        square: {_x000D_
          red: "SquareRedFile",_x000D_
          blue: "SquareBlueFile"_x000D_
        }_x000D_
      };_x000D_
      var filename = Test01[whatOption][whatColor];_x000D_
      alert(filename);_x000D_
    }_x000D_
  </script>_x000D_
</head>_x000D_
<body>_x000D_
  <p onclick="displayFile('rectangle', 'red')">[ Rec Red ]</p>_x000D_
  <br/>_x000D_
  <p onclick="displayFile('square', 'blue')">[ Sq Blue ]</p>_x000D_
  <br/>_x000D_
  <p onclick="displayFile('square', 'red')">[ Sq Red ]</p>_x000D_
</body>_x000D_
</html>

_x000D_

User · Answer

You don t need a function for it - simply use the bracket notation   var side   columns  right      This is equal to dot notation  var side   columns right   except the fact that right could also come from a variable  function return value  etc   when using bracket notation   If you NEED a function for it  here it is   function read prop obj  prop        return obj prop         To answer some of the comments below that aren t directly related to the original question  nested objects can be referenced through multiple brackets  If you have a nested object like so   var foo     a  1  b  2  c   x  999  y 998  z  997      you can access property x of c as follows   var cx   foo  c    x     If a property is undefined  an attempt to reference it will return undefined  not null or false    foo  c    q       null    returns false  foo  c    q       false    returns false  foo  c    q       undefined    returns true

User · Answer

ThiefMaster s answer is 100  correct  although I came across a similar problem where I needed to fetch a property from a nested object  object within an object   so as an alternative to his answer  you can create a recursive solution that will allow you to define a nomenclature to grab any property  regardless of depth   function fetchFromObject obj  prop         if typeof obj      undefined             return false             var  index   prop indexOf          if  index  gt  -1            return fetchFromObject obj prop substring 0   index    prop substr  index   1               return obj prop       Where your string reference to a given property ressembles property1 property2  Code and comments in JsFiddle

[javascript] JavaScript object: access variable property by name as string

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