JSFiddle - React, Tailwind, and code Playground

HTML

<a href="http://www.example.com?iframe">ayres</a>
<a href="http://www.example.com?if=1">nfo</a>
<a href="http://www.example.com?iframe=1">ryes</a>
<a href="http://www.example.com?if=1">no</a>
<a href="http://www.example.com?iframe&sortby=awesomeness">yes</a>

JavaScript

(function($) {

  $.fn.tagName = function() {
    return this.get(0).tagName.toLowerCase();
  }

  $.expr[':'].inHRef = function(obj, index, meta, stack){
  
    if ($(obj).tagName() != 'a')
      return false;
  
    // Regular Expression
    
    var rgCI = '\\'+$(obj).attr('href') + '\\gi';
    
    // case-insensitive
    return (rgCI.match(meta[3]));
    
    var rgCS = '\\'+$(obj).attr('href') + '\\g';
    
    // case-sensitive
    //return (rgCS.match(meta[3]));
    
    // IndexOf
    
    // case-insensitive
    //return ( $(obj).attr('href').toLowerCase().indexOf(meta[3].toLowerCase()) > -1);
        
    // case-sensitive
    //return ( $(obj).attr('href').indexOf(meta[3]) > -1);
    
};

})(jQuery);

$(function() {
    
    $('a:inHRef(iframe)').css('background-color', '#aaaaa0');
    
});