JSFiddle - React, Tailwind, and code Playground

HTML

<form id="form_id" action="#">
  <a data-prefix-age="22">22</a>
  <a data-prefix-weight="82">82</a>
  <a data-prefix-foo="82">82</a>
  <a href="#">meh</a>
</form>

JavaScript

$(function(){
        // retrieve all elements within the `#form_id` container
        var $formElements = $("form#form_id > *");

        var selectedElements = [];
        // iterate over each element
        $formElements.each(function(index,elem){
            // store the JavaScript "attributes" property
            var elementAttr = $(this)[0].attributes;
            // iterate over each attribute
            $(elementAttr).each(function(attIndex,attr){
                // check the "nodeName" for the data prefix
                if (attr.nodeName.search('data-.*') !== -1){
                   // we have found a matching element!
                   if (selectedElements.length < 2){
                     selectedElements.push(elem);
                   }
                }
            });
        });
        console.log(selectedElements);
});