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One, variable
Javascript has five basic data types number, String, boolean, undefined, null a composite type: Object
Second, using the getElementById method to obtain the element
Way One:
Here the element, refers to the HTML tag, through the built-in docuement ' getElementById ' method to get the element that set the id attribute on the page, get an HTML object, and assign a value to it,
Do not assign a value to see an example:
<!DOCTYPE HTML><HTMLLang= "en"><Head> <Scripttype= "Text/javascript"> varDiv1=document.getElementById ('Div1'); </Script></Head><Body> <DivID= ' Div1 'title= "This is a label">The IS label</Div></Body></HTML>
Then open the browser, the mouse point on the label (DIV1) above: There will be a hint, this is the DIV1 this element of the title stored information
Then the title of the tag is modified by the acquisition, but the following method will fail, because the page scanning way from top to bottom, first scan the non-existent variables can not be changed, will error.
<!DOCTYPE HTML><HTMLLang= "en"><Head> <Scripttype= "Text/javascript"> varDiv1=document.getElementById ('Div1'). Title= 'I got it!'; </Script></Head><Body> <DivID= ' Div1 '>The IS label</Div></Body></HTML>
So, put the script under the div tag.
<!DOCTYPE HTML><HTMLLang= "en"><Head> <Scripttype= "Text/javascript"> </Script></Head><Body> <DivID= ' Div1 '>The IS label</Div> <Scripttype= "Text/javascript">document.getElementById ('Div1'). Title= 'I got it!'; </Script></Body></HTML>
Effect of modifying title
If you change the <script> in the
<!DOCTYPE HTML><HTMLLang= "en"><Head> <Scripttype= "Text/javascript">window.onload= function() {document.getElementById ('Div1'). Title= 'I got it!'; } </Script></Head><Body> <DivID= ' Div1 '>The IS label</Div> </Body></HTML>
Iii. Elements of Operation
JS can be modified by acquiring elements and attributes of elements;
---operation method: 1, the operation of the point: '. ' ；
2, parentheses operation: ' [] ';
---Property modification method: 1, JS, the property of the same notation as HTML;
Example 1: Modifying properties:
<!DOCTYPE HTML><HTMLLang= "en"><Head>window.onload = function () {var input = document.getElementById (' input1 '); var target = document.getElementById (' Text1 '); attribute var val = input.value; var type = Input.type; var name = Input.name; Change attribute Target.style.color = ' red '; Target.style.fontSize = ' Val '; } </Script></Head><Body> <inputtype= "text"name= "SetSize"ID= "INPUT1"value= "20px"> <H1ID= "Text1">SetSize</H1> </Body></HTML>
effect, below the SetSize
Getting Started with JavaScript (ii) variables, getting elements, manipulating elements
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