Three methods for writing Javascript event processing code

1. event handler as the HTML property value

HTML code
<Input name = "btn" type = "button" id = "btn" value = "button" onclick = "alert ('mzwu. com');"/>
 

 

2. event handler as a JavaScript property

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HTML code
<Input name = "btn" type = "button" id = "btn" value = "button"/>
<Script language = "javascript">
Document. getElementById ("btn"). onclick = function () {alert ("mzwu.com ");}
</Script>
 

 

Note: The first method may mislead you to write it as document. getElementById ("btn "). onclick () = "alert ('mzwu. com '); ", this write is incorrect! In fact, the first method implicitly creates a function, which can be described using the following code, because it detects that the HTML attribute value is actually a function:

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HTML code
<Input name = "btn" type = "button" id = "btn" value = "button" onclick = "alert (typeof (this. onclick);"/>
 

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The above Code uses a direct volume to create a function and changes it to the function () Statement:

HTML code
<Input name = "btn" type = "button" id = "btn" value = "button"/>
<Script language = "javascript">
Function e ()
{
Alert ("mzwu.com ");
}
Document. getElementById ("btn"). onclick = e;
</Script>
 

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Therefore, we can extend the third method.

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3. Method 3

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HTML code
<Input name = "btn" type = "button" id = "btn" value = "button"/>
<Script language = "javascript">
Function document. all. btn. onclick ()
{
Alert ("mzwu.com ");
}
</Script>
 

Note: such methods include function document. onclick () {}, but this method is only feasible in IE and FF tests, and then changed to function document. getElementById ("btn "). onclick () {} does not work in IE or FF. It is not difficult to explain the lack of identifiers, because the JavaScript identifiers do not allow dot numbers. document is used. getElementById ("btn "). the onclick identifier is obviously incorrect, but the document. all. btn. onclick is a bit confusing.