javascript allows array[0] values to be referenced as an object [closed]

I am going through an old app cleaning and aligning code and came across an array element being referenced as an object and am wondering how it is working.

Specifically, an array is being returned from an API in the following format:

//PHP
$returnInfo[] = array("success"=>true,"reviews"=>$reviews,"iCount"=>$resCount) ;
...
sendResponse(200, json_encode($returnInfo));

//JS
service.getReviews
.then(function(response) {
   let resData = response.data ;
   console.log(resData) ;

   // prints to console
   //
   // [{…}]
   //      0: 
   //          iCount: 0
   //        > reviews: (3) [{…}, {…}, {…}]
   //          success: true
   //        > [[Prototype]]: Object
   //        length: 1
   //      > [[Prototype]]: Array(0)
   // 

   var allReviews = null ;
   if (resData.iCount == 0) { 
      allReviews = resData.reviews ;
   }

My expectation is that this would have thrown an error because it should be referenced as:

var allReviews = null ;
if (resData[0].iCount == 0) { 
   allReviews = resData[0].reviews ;
}

So how is the object reference working?

I changed the code in the app to use resData[0].iCount and resData[0].reviews and it continues to work – so its working in both formats and I don’t understand how. Those array[0] values do not exist at the root of the array or outside the element list so how can they still be referenced as a traditional object?

On a side note, I have found several instances of this working in the app but am unable to replicate the issue using online JS testing sites like jsbin (.) com. As well, in my google searches I have not found any threads/articles that is explaining what I am seeing.