文字框失去焦點樣式改變

<input type="text" value="" placeholder="請輸入">
  <script>
    var input = document.querySelector('input');
  
    
    // 獲取焦點：onfocus
    // 失去焦點：onblur
    

        
        input.onblur = function() {
            if(this.value==''){
                this.style.background = 'pink';
            }
        
        } 
   
    
    
  </script>