Accessing JSON object with key from a string array using dot operator in JS not working

Question

The JSON object I got was from another PHP file that is called through $.ajax(). For example, I returned from my PHP file a echo json_encode(array('a' => 'b')).

Then, I have the following $.ajax() code:

let objKey = ['a'];

$.ajax({
  type        : 'POST',
  url         : 'phpfilehere.php',
  dataType    : 'json',

  success     : function(obj) {
      alert(obj.objKey[0]);
  }
});

It should have alerted b instead of undefined. Then, I tried alert(obj.a) and it worked. It alerted b. How do I access the value of the JSON object with an array of string which all corresponds to the key of said JSON object?

Use `obj[objKey[0]]` instead, for more information [see this](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Property_accessors#Syntax) — HMR, Feb 18 '19 at 10:06
Hm how will that fix it? Shouldn't it be the same as using the dot operator? — Richard, Feb 18 '19 at 10:07
@HMR How is it different then? Could you please provide an answer below? — Richard, Feb 18 '19 at 10:09
Dot operator expects _**exact**_ property name after object and does **not evaluate** variables. So `obj.objKey` accesses property of `obj` named `objKey`. — hindmost, Feb 18 '19 at 10:18
@hindmost THAT is exactly what I was looking for. Thank you hindmost. — Richard, Feb 19 '19 at 06:59

R3tep · Accepted Answer · 2019-02-18T10:17:37.890

1

obj.objKey[0] is false in your case, it's good if your object is like :

obj = { 'objKey': ['b'] }

You have two solutions in your case

alert(obj[objKey[0]]);

or

alert(obj.a);

Reference

Property Accessors MDN

edited Feb 18 '19 at 10:17

answered Feb 18 '19 at 10:09

R3tep

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Accessing JSON object with key from a string array using dot operator in JS not working

1 Answers1