How to monitor js

In Javascript, browsers are generally divided into two categories:

① Browsers based on the IE kernel (IE browsers with version numbers less than 9)

② Browsers based on the W3C kernel Browser (IE browser, Firefox, Google and other browsers with version number greater than 9)

1) Basic syntax: Based on IE kernel browser

dom object.attachEvent(type, callback, capture): Bind event listener to element

Parameter description:

type: Binding Event types, such as onclick, onmouseover, onmouseout

callback: event handler, usually an anonymous function

capture: the browser model used, bubble model and capture model, default Browsers below IE8 only support the bubbling model!

2) Basic syntax: event listening based on W3C kernel

dom object.addEventListener(type, callback): Bind event listening for W3C kernel browser

Parameter description:

type: Binding event type, without 'on' prefix, such as click, mouseover, mouseout

callback: event processing Program, usually an anonymous function

2. Summarize the difference between event monitoring

The monitoring method of the IE kernel and the W3C kernel Listening method:

①Different methods

The browser with IE core uses attachEvent for binding

The browser with W3C core uses addEventListener for binding

②The parameters are different

IE kernel browser, its binding method has three parameters type, callback, capture (browser model used)

W3C kernel browser, its binding method There are two parameters in total, type and callback

③The type parameter is different

For browsers with IE core, type needs to be prefixed with 'on', such as onclick

W3C core Browsers, type does not need to add the 'on' prefix, such as click

④The triggering order is different

In browsers with IE kernel, the event monitoring is bound first, then triggered, and then bound Determined to trigger first

W3C kernel browser, its event monitoring is bound first and triggered first, then bound and then triggered

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