How does jquery determine whether an element has a specified style?

There are two scenarios:
1. If css is written as an in-row style, you can determine it by obtaining the value of the style attribute, for example:
Determine whether the div element with id divid has a font-size style:
Copy codeThe Code is as follows:
<Div id = "divid" style = "float: left; font-size: 12px;"> </div>
The jquery code is as follows:
JQuery ("# divid"). each (function (){
Var fontSize = $ (this). attr ("style"). indexOf ("font-size ");
If (fontSize! = (-1) {alert ("defined ");}
Else{((this).css ({"float": "left", "font-size": "12px "});}
});

Note: if there is only one div element whose id is divid, jquery's each is executed only once.
2. If css is written as a class style, you can determine it by obtaining the value of the class attribute, for example:
Determine whether the div element with the id divid contains the class style divclass:
Copy codeThe Code is as follows:
. Divclass {
Background-color: # F33;
}
<Div id = "divid" class = "divclass"> </div>

The jquery code is as follows:
Copy codeThe 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 allows you to click to switch the background color.