Superação

css

.wp-search-form {
  clear: both;
  padding: 20px;
  background-color: #EAEAEA;
  overflow: hidden;
}

.text-wrapper {
  
  display: inline-block;
}

.search-wrapper {
  margin-left: 10px;
  display: inline-block;
}

js

function getQueryString() {
  // This function is anonymous, is executed immediately and 
  // the return value is assigned to QueryString!
  var query_string = {};
  var query = window.location.search.substring(1);
  var vars = query.split("&");
  for (var i=0;i<vars.length;i++) {
    var pair = vars[i].split("=");
        // If first entry with this name
    if (typeof query_string[pair[0]] === "undefined") {
      query_string[pair[0]] = decodeURIComponent(pair[1]);
        // If second entry with this name
    } else if (typeof query_string[pair[0]] === "string") {
      var arr = [ query_string[pair[0]],decodeURIComponent(pair[1]) ];
      query_string[pair[0]] = arr;
        // If third or later entry with this name
    } else {
      query_string[pair[0]].push(decodeURIComponent(pair[1]));
    }
  } 
    return query_string;
};

function replaceUrlParam(url, paramName, paramValue){
    var pattern = new RegExp('\\b('+paramName+'=).*?(&|$)')
    if(url.search(pattern)>=0){
        return url.replace(pattern,'$1' + paramValue + '$2');
    }
    return url + (url.indexOf('?')>0 ? '&' : '?') + paramName + '=' + paramValue 
}

function searchHandler(){
    var searchText = jQuery("#search-text");
	var searchTerm = searchText.val();
	var location = replaceUrlParam(window.location.href, 'keyword', searchTerm);
	document.location = location;
};

jQuery(function() {
  
  var queryString = getQueryString();
  console.log(queryString);
  
  jQuery('.sell-media-breadcrumbs').after('<div class="wp-search-form"></div>');
  var searchForm = jQuery(".wp-search-form");
  searchForm.append('<div class="text-wrapper"><input type="text" id="search-text"/></div>');
  
  var searchText = jQuery("#search-text");
  searchText.on('keypress', function(event) {
	if(event.which == 13) {
	  searchHandler();
	}
  });
  searchText.val(queryString['keyword']);
  
  searchForm.append('<div class="search-wrapper"><button id="search-btn">Pesquisar</button></div>');
  var searchBtn = jQuery("#search-btn");
  searchBtn.click(searchHandler);
});