How does jquery determine if an element has the specified style

It can be divided into the following two situations:
1. If the CSS is written as inline style, it can be judged by obtaining the value of the style attribute, as shown in the following example:
Determine whether the div element with id divid has a font-size style:

 
<div id="divid" style="float:left; font-size:12px;"></div> 
jquery The code is as follows:  
jQuery("#divid").each(function(){ 
var fontSize = $(this).attr("style").indexOf("font-size"); 
if(fontSize != (-1)){alert(" The defined ");} 
else{$(this).css({"float":"left","font-size":"12px"});} 
}); 

Note: if there is only one div element with id divid, jquery's each is executed only once.
2. If the CSS is written as a class style, it can be judged by getting the value of the class attribute, as shown in the following example:
Determine whether the div element with id divid contains the class style divclass:

 
.divclass{ 
background-color: #F33; 
} 
<div id="divid" class="divclass"></div> 

The jquery code is as follows:

 
jQuery("#divid").click(function(){ 
if(jQuery(this).attr("class").indexOf("divclass")>0){ 
jQuery(this).removeClass("divclass") 
}else{ 
jQuery(this).addClass("divclass") 
} 
}); 

Note: the above code can be clicked to switch the background color.