function inputDeal(elem) {
var searchButton=document.getElementById('search-button');
if (elem.value == '') {
searchButton.disabled=true} 
else {
searchButton.disabled=false;}
}
window.onload=function() {
    if (document.getElementById('search-input')!=null) {
     var searchInput=document.getElementById('search-input');
     searchInput.onchange=function(){inputDeal(searchInput)};
     searchInput.onkeyup=function(){inputDeal(searchInput)};
     }
}