实现网页屏蔽Backspace事件，输入框不屏蔽

document.onkeydown = function (e) { var code; if (!e) { var e = window.event; } i

document.onkeydown = function (e) {    var code;    if (!e) {        var e = window.event;    }    if (e.keyCode) {        code = e.keyCode;    }    else if (e.which) {        code = e.which;    }    alert(event.srcElement.type);    //BackSpace 8;    if (        (event.keyCode == 8)        && ((event.srcElement.type != "text" && event.srcElement.type != "textarea" && event.srcElement.type != "password")            || event.srcElement.readOnly == true        )    ) {        event.keyCode = 0;        event.returnValue = false;    }    return true;}