DOM 中的类定义在 javascript 中连接

Question

I don't know what is different between (I) and (II) ? whether these class is same for use in a (js file/css file) or not different ?

I: <div class="start-box active">

II: <div class="start-box">

Answer 1

in I you have two class start-box and active but in II you have just one class. you can use js to add or delete class from element. and with css you can set some css property for the active when use event handler you can read this link HTML Event Attributes

Answer 2

The class name attribute of an element accepts a single class name, or a space separated list of class names.

So in

<div class="start-box active">

the div element has two classes, start-box and active , whereas in

<div class="start-box">

the div element is only assigned the one class, start-box .

The combination of multiple classes on one element, or even the effect of a single class on an element given its relationship to other elements, is subject to the rules of cascading style sheets (meaning "CSS") .

I wish you well in learning more about CSS - you may find that the article "Learn to style HTML using CSS"]( https://developer.mozilla.org/en-US/docs/Learn/CSS ) on MDN useful in doing so.