html input标签使光标移动到文本的最后面

var content = "input元素";
 content.focus(); 
 var len = content.value.length;
 if (document.selection) {  
  var sel = content.createTextRange();  
  sel.moveStart('character', len);  
  sel.collapse();  
  sel.select(); 
 } else if (typeof content.selectionStart == 'number' && typeof content.selectionEnd == 'number') {
  content.selectionStart = content.selectionEnd = len; 
 }