DOM - Event Object

Event Object:

If given an event of an element object (such as onclick) binds a response function (callback function), which is called by the browser when the event is triggered.and browsercreates an object to describe this event.

When the event is triggered, the handler function will pass in data - the information when it is triggered.

When the mouse event fires:

altKey When the mouse event occurs, whether to press the alt key, return a boolean
ctrlKey When the mouse event occurs, whether to press the ctrl key, return a boolean
metaKey When the mouse event occurs, whether to press the windows/commond key, return a boolean
shiftKey When the mouse event occurs, whether to press the shift key, return a boolean
pageX The X coordinate of the mouse click; (including the body hidden)
pageY The Y coordinate of the mouse click;(including body hidden)
clientX clientY returns the coordinates of the mouse position relative to the upper left corner of the browser window, in pixels (excluding body hidden)
screenX screenY returns the coordinates of the mouse position relative to the upper left corner of the screen,The unit is pixel
movementX, movementY returns a displacement value, the unit is pixel, indicating the distance between the current position and the last mousemove event
offsetX/offsetY is relative to the element's own x/y and whether it is positionedElement independent

When the keyboard event fires:

charCode/keyCode key code value key key code (left 37, top 38, right 39, bottom 40, enter 13)

This in the event points to:

1. Inline: When inline binding, the inline environment object is btn The caller of the function is window and the event object cannot be obtained.

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2. Element attributes: this points to the dom element itself, and the event object is in the parameter.

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3.addEventListener: this points to the dom element itself, and the event object is in the parameter.

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