JavaScript：非输入框禁用退格键

在js文件或<javascript>标签中加入如下代码：

 /**
 *非输入框禁用退格键
 */
 function banBackspace(e)
 {
     var ev = e || window.event;
     var field = ev.target || ev.srcElement;
     var fieldType = field.type || field.getAttribute('type');
     var isReadOnly = field.readOnly;
     var isDisabled = field.disabled;
     isReadOnly = (isReadOnly == undefined) ? false : isReadOnly;
     isDisabled = (isDisabled == undefined) ? true : isDisabled;

     var KEY_BACKSPACE = 8;
     var inputFieldTypes = [ 'password', 'text' , 'textarea'];

     var isOnReadonlyOrDisabledField = inputFieldTypes.containsArr(fieldType) && (isReadOnly || isDisabled);
     var isNotOnAnyField = !inputFieldTypes.containsArr(fieldType);

     if (ev.keyCode == KEY_BACKSPACE && (isOnReadonlyOrDisabledField || isNotOnAnyField)) {
          return false ;
     }
 }
 document.onkeydown = banBackspace;