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;