Edit in JSFiddle

window.onload = function() {
   var hit = document.getElementById('hit'),
       btn = document.getElementById('btn');
    btn.onclick = function() {
      //hit.disabled = true; 
      hit.readOnly = true; 
      hit.style.cursor='not-allowed';  
      hit.onfocus = function() {
        this.blur();
      }    
    }
      
}

<input type='text'  id='hit'/> 
<button type='button' id='btn'>禁止输入</button>