使用这个搜索整个页面

if($('*').hasClass('mydivclass')){
// Do Stuff
}

var x = document.getElementsByClassName("class name");
if (x[0]) {
alert('has');
} else {
alert('no has');
}

Javascript中最好的方法:

if (document.getElementsByClassName("search-box").length > 0) {
// do something
}

要显式地测试div元素:

如果($ (' div.mydivclass”)。长度){…}

if($(".myClass")[0] != undefined){
  // it exists
}else{
  // does not exist
}

这里有一些方法:

1.  if($("div").hasClass("mydivclass")){
    //Your code

    //It returns true if any div has 'mydivclass' name. It is a based on the class name
    }

2. if($("#myid1").hasClass("mydivclass")){
    //Your code


    //  It returns true if specific div(myid1) has this class "mydivclass" name. 
    //  It is a  based on the specific div id's.
    }           
3. if($("div[class='mydivclass']").length > 0){
    //Your code

   // It returns all the divs whose class name is "mydivclass"
   //  and it's length would be greater than one.
    }

我们可以根据需要使用任何一种abobe定义的方法。