Problem with JQuery function: Uncaught ReferenceError

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Javascript

jQuery

Hi,
I have written a function that returns an Array of elements from one div and each element has an Array of attributes (ID, position, type(image or text) and text or image source). I think the main problem is, that I am generating a selector in the runtime from the ID - $(#Counter).text() in for cycle and instead of a selector I have written there the variable selector.toString(), but it gives me for example a position normally, but it doesn't give the class - instead of some type, there is written undefined. And in this if condition it throws this error: Uncaught ReferenceError: Invalid left-hand side in assigment

if ($(selector.toString()).children().first().css("class") = "img") {

How to fix this error or how fix the whole function to do what I want?
Here is the whole function commented:

function getAllElements() {
            var elems = new Array();    //creates new Array for all elements in div "platno".
            for (var i = parseInt("0"); i < parseInt($("#Counter").text()); i++) {
                var selector = "#" + i; //creates a selector from actual i, which represents ID.
                var elem = new Array(); // creates an Array for all attributes of an element
                elem[0] = i;    //first is ID
                elem[1] = $(selector.toString()).position();    //second is position
                elem[2] = $(selector.toString()).children().first().css("class"); //third is class (text or image)
                if ($(selector.toString()).children().first().css("class") = "img") {
                    elem[3] = $(selector.toString()).children().first().css("src");  //fourth is image source
                }
                else {
                    elem[3] = $(selector.toString()).children().first().text;   //or fourth is text of an element
                }
                elems[i] = elem;    // adds an element to Array of all elements
            }
            return elems;   //returns all elements
        }

Thanks a lot for good solutions!

Pepin z Hane