防止鼠标右键复制文字代码 简单易用

防鼠标右键复制代码，需要拿走，

    document.onkeydown = function(){
    if(window.event && window.event.keyCode == 123) {
        alert("浏览器搜索【南图博客】即可访问本站");
        event.keyCode=0;
        event.returnValue=false;
    }
    if(window.event && window.event.keyCode == 13) {
        window.event.keyCode = 505;
    }
    if(window.event && window.event.keyCode == 8) {
        alert(str+"\n请使用Delete键进行字符的删除操作！");
        window.event.returnValue=false;
    }
}
document.oncontextmenu = function (event){
    if(window.event){
    event = window.event;
    alert("请记住本站永久域名【www.nta6.com】");
    }
    try{
    var the = event.srcElement;
        if (!((the.tagName == "INPUT" && the.type.toLowerCase() == "text") || the.tagName == "TEXTAREA")){
        return false;
        }
        return true;
    }
    catch (e){
        return false;
    }
}

效果别人点击右键会跳出