javascript - 在输入框获得焦点时禁用 IE8 中的 F5 Ctr+F5 和 Ctrl+R

Question

我想在文本框聚焦时禁用网页刷新我正在使用的代码是这对其他快捷方式非常有用，除了：

顺便说一句，我想通过纯 JavaScript 没有 JQuery 和没有 JavaScript 框架来实现这一点。

  document.onkeydown = keyDown  //control chars
document.onkeypress = keyDown   //any char/number

function keyDown(e) {

        //74=j, 75=k, 78=n, 84=t
        var forbiddenCtrlKeys = new Array(74,75,78, 84);
        //37=left_arrow, 39=right_arrow
        var forbiddenAltKeys = new Array(37,39);
        //8=backspace, 116=F5
        var forbiddenSingleKeys = new Array(8,116);
        //per le textbox 116=F5
        var forbiddenTextBoxKeys = new Array(116);

        key = window.event.keyCode;     //IE

              if(window.event.ctrlKey){ //ctrl
                    isCtrl = true;
                    isAlt = false

                    checkVal(forbiddenCtrlKeys,window.event.keyCode);
              }
              else if(window.event.altKey){ //alt
                    isCtrl = false;
                    isAlt = true;
                    checkVal(forbiddenAltKeys,window.event.keyCode);
              }

              else{ //other

                    isCtrl = false;
                    isAlt = false;
                    var element = e.target.nodeName.toLowerCase();
                    var curr = document.activeElement
                    if(curr.tagName=="INPUT")
                    alert(curr.tagName);

                    if((element != 'input' && element != 'textarea') || $(e.target).attr("readonly")){
                        alert(window.event.keyCode);
                        checkVal(forbiddenSingleKeys,window.event.keyCode); 
                    }
                    if(document.event.keyCode==116){
                        alert(window.event.keyCode);
                        document.event.keyCode=0;
                        checkVal(forbiddenTextBoxKeys,window.event.keyCode);
                    }       
              }
}

function checkVal(set,key){


        for(i in set)
        {
        //case-insensitive comparison
            if(String.fromCharCode(set[i]).toLowerCase() == String.fromCharCode(key).toLowerCase())
                        {
                                alert('This key combination has been disabled.');
                                window.event.returnValue =        false;    
                                window.event.keyCode = 0;
                                return true;
                        }
        }
}

所以我在其他情况下试图实现的是每当我尝试按 F5 禁用它但它不起作用时，任何洞察力将不胜感激