Detailed explanation of examples of className and a href

JS and a href

In the href, pay attention to the end of the semicolon and the closing quotation marks

<a>空链接</a><a>弹出</a>

Generally, it is okay to leave the code, usually leave it empty. You can also use the pound sign '#' if it is empty, but it is not very good.

className

<style>#div1 {width:100px; height:100px; border:1px solid black;}.box {background:red;}</style><script>function toRed()
{var oDiv=document.getElementById(&#39;div1&#39;);
    
    oDiv.className=&#39;box&#39;;             //不要写成class
}</script><input><div></div><p>1. getelementbyId is connected to id. But there is no method connected to class. </p>

getElementById()	Returns a reference to the first object with the specified id.
getElementsByName()	Returns a collection of objects with the specified name.
getElementsByTagName()	Returns a collection of objects with the specified tag name.

Use JS to create an index style based on className. You need to add a secondary attribute '.className' after getelement.

After adding it, the tag with the originally specified id will not only be indexed from the 'pound sign' The style of the id is also indexed from the 'dot' index to the style of the class.

2. Changes caused by getelement.className = 'box'; :                                           The example is oDiv, which is the same as another way of saying it.

If the

tag already has the attribute class=xxx, then when the event action leads to the function, class=xxx will be modified to class=box

If

does not have class =xxx, it will be created incidentally when executing the script.

Recall that if

does not have a specified style = XXX, then getelement.style .backgroud will also automatically create

getelement. + style/ class / type / href / value etc. You can change or add them as you like. I’m afraid you don’t want to change

This is just a method.

- There is also getelement ['value'], which uses square brackets and quotes, which are the same as . (dot) to bring out attributes. Generally, it will not be used except in special circumstances. [' '] This way.

If [''] refers to a variable assuming a ='width', then ['a'] becomes [' ' width ' '] like this It does not conform to the concept of getelement ['attribute'].

The processing method at this time can be [a] without quotation marks!

- All. can be used [''] instead of

oDiv.className='box '; //The following are equivalent

oDiv['className'] = 'box';

Multiple layers are also available, oDiv['style'][' width'] = '40px'

- When do you need to use ['']? Function parameters can generally be passed to the value. Sometimes, they need to be passed to the attribute name to represent the attribute. In this case, To use ['']

JS embedded html running sequence:

-execute event action, execute the pointed JS Function, the function modifies the specified id tag.

JS embedded html code writing sequence:

-Think about the effect of the change, mark id/class to the specified effect Tag, use . or # to create {style}, call ID to write the logic of changing css, and trigger it with event function.

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