Detailed explanation of the process of writing JS

html +css Static page

js Dynamic interaction

Principle: js is to modify the style, such as popping up a dialog box. The pop-up process is that the box is disabled Change it to display:enable. Or change the color when the mouse points to it. It is a tool to modify the style.

• The process of writing JS

• Layout: HTML+CSS

• Event: Determine what actions users do (product design)

• Write JS: In the event, use JS to modify the style of the page element(Additional attributes: determine which attributes to modify )

• What is an event

A complete event = >

Scope: Action tag

Event statement: a user operation, for example: mouse in and out onmouseover, onmouseout,

Function action: a well-encapsulated action that can be understood as a more complex action.

The event statement is also a certain part of this scope An attribute, a function is a series of actions made by this attribute

• function Standard location and encapsulation

Format:

<script></script>

function+name+()

{action 1+action 2+action 3+……}

Position: <script>: Js code tag, the function is generally placed in the head Inside.</script>

Encapsulation:

Function: fuction+name+()

1. ##Placing unencapsulated code in tags will cause visual confusion for readers. Encapsulate the entire code into a function, and then call the function in the tag. The document will become cleaner.

2. When multiple tags call the same function repeatedly, no need Type the entire code again, just call the name of the function.

Variables: var + name + ()

Variables are to combine some complex structures Assigning the object to a simple name will reduce the amount of code when called.

##​ oDiv.style.width= oDiv.style.height= oDiv.style.background='green'

<script><strong></script>

#function toGreen()

{

##​

var oDiv=document.getElementById('div1');Action 1: div1 assigns the value 2 to oDiv

'300px'

; Action 2/3 changes the width of div1

'300px'

;

;

Action 4, the background turns green

}

##> ;

Note, if there are statements in the script that are not to be run yet, you can //comment out

Detailed explanation of function action hierarchical structure and explanation of Document.getElementById: (Key points)

Object properties are divided into many layers, and each layer is separated by '.' .What follows is the previous sub-attribute (attribute), which can be understood as '的' in Chinese

In fact, each function action is divided, so what you see is section by section. Actually, for example

oDiv.style.width='300px'; this action belongs to:

Document.getElementById('div1').style.width = '300px' And this entire paragraph belongs to:

Window.Document.getElementById('div1').style.width = '300px'

##NodeNodeNodeNode

window is omitted because we operate in html, which defaults to document

. And because we defined oDiv, the final expression becomesoDiv.style.width='300px'; form.

##As for Document, it is a JS The basic nodes of the document are controlled by the method of operating the document level (action method). These nodes include text nodes and label (attribute) nodes. All ranges outside the angle brackets become text nodes, angle brackets The foot attribute node inside. If we don’t say what node it is, it usually refers to the one inside the angle brackets by default.

DOM (Document object):

(The method is the action we described above)

This entire is a complete eventaction,

window is the upper-level object

document is the second-level object

getElementById is a three-layer object (method)

styleFour-layer object (first-layer attribute)

##height Five-layer object (second-layer attribute)

div1 {width:200pxheight:200pxbackground:

# #

##

# charset="utf-8" >

##​

;

​

;

   

red

; }

#

##<script></script>

function toGreen()

{ 

    var oDiv=document.getElementById('div1');

     

    oDiv.style.width='300px';

    oDiv.style.height='300px';

    oDiv.style.background='green';

} 

function toRed()

{ 

    var oDiv=document.getElementById('div1');

     

    oDiv.style.width='200px';

    oDiv.style.height='200px';

    oDiv.style.background='red';

} 

id="div1" onmouseover="toGreen()" onmouseout="toRed()">