JS 禁用IE快捷键

[qq_29026265]

JS 代码禁用IE快捷键后，触发两次，一次自己写的代码提示，第二次IE自带快捷键触发
故如何做到只触发一次自己写的代码？
if (event.keyCode == 122){
alert("d");
event.returnValue = false;
}

[天际的海浪]

event.preventDefault()

[天际的海浪]

window.addEventListener("keydown", function (e) {
    if (e.keyCode == 122){
        alert("d");
        e.preventDefault();
    }
}, false);

[qq_29026265]

正确的是： document.onkeydown = function(e) { var isie = (document.all) ? true: false; var key; var ev; if (isie) { key = window.event.keycode; ev = window.event; } else { key = e.which; ev = e; } if (key == 112 || key ==113 || key ==114 || key ==115 || key ==116 || key ==117 || key ==118 || key ==119 || key ==120 || key ==121 || key ==122 || key ==123) { if (isie) { ev.keycode = 0; ev.returnvalue = false; return false; } else { ev.which = 0; return false; } } };