if(document.all){
document.onselectstart= function(){return false;}; //for ie
}else{
document.onmousedown= function(){return false;};
document.onmouseup= function(){return true;};
}
document.onselectstart = new Function(‘event.returnValue=false;‘);
原文：https://www.cnblogs.com/holy-amy/p/10200558.html