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JavaScript Basics, Login verification

Source: Internet
Author: User
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    1. Three ways to use <script></script>:
      2. Put in the <body>
      4. Put in the
      5. Placed in an external JS file
        <!DOCTYPE HTML><HTMLLang= "en"><Head>    <MetaCharSet= "UTF-8">    <title>Text1</title>    <Script>        functiondisplaydate () {document.getElementById ("Text1"). InnerHTML=Date (); }    </Script>    <Scriptsrc= "1.js"></Script></Head><Body>      <P>Hello</P>      <Script>document.write (Date ()) document.getElementById ("Demo"). InnerHTML=Date (); </Script>  <Buttontype= "button"onclick=window.alert ("User name cannot start with a number")>button</Button></Body></HTML>

    2. Three ways to output data:
      2. Use the document.write () method to write content to an HTML document.
      4. Use the Window.alert () pop-up warning box.
      5. Writes to an HTML element using InnerHTML.
        2. Use the ID property to identify the HTML element.
        4. Use the document.getElementById (ID) method to access HTML elements.
        5. Use innerHTML to get or insert element content.
          <!DOCTYPE HTML><HTMLLang= "en"><Head>    <MetaCharSet= "UTF-8">    <title>Text2</title></Head><Body>      <PID= "Text2">111</P>      <Script>document.getElementById ("Demo"). InnerHTML=Date (); </Script>  <Buttontype= "button"onclick=window.alert ("User name cannot start with a number")>button</Button></Body></HTML>

    4. The login page prepares:
      1. Add an Error prompt box.
      2. Write a good html+css file.
      3. Set the ID of each INPUT element
    6. Defines a JavaScript function.
      1. Verify user name 6-20-bit
      2. Verify password 6-20-bit
    7. The onclick invokes this function.
      <!DOCTYPE HTML><HTMLLang= "en"><Head>    <MetaCharSet= "UTF-8">    <title>Text3</title>    <Linkrel= "stylesheet"type= "Text/css"href=".. /static/css/123.css ">    <Script>        functionFnlogin () {varOuname=document.getElementById ("uname"); varOupass=document.getElementById ("UPass"); varOerror=document.getElementById ("Error_box"); if(OUname.value.length< 6 ||OUname.value.length>  -) {oerror.innerhtml= "Please enter a 6-20-digit user name"            }            if(OUpass.value.length< 6 ||OUpass.value.length>  -) {oerror.innerhtml= "Please enter a 6-20-digit password"            }            if((OUname.value.length< 6 ||OUname.value.length> Ten) &&(OUpass.value.length< 6 ||OUpass.value.length>  -) ) {oerror.innerhtml= "Please enter a 6-20-digit user name and password"            }        }    </Script></Head><Body><Divclass= "box">    <H2>Login</H2>    <Divclass= "Input_box">        <inputID= "Uname"type= "text"placeholder= "Please enter user name">    </Div>    <Divclass= "Input_box">        <inputID= "UPass"type= "text"placeholder= "Please enter password">    </Div>    <DivID= "Error_box"><BR></Div>    <Divclass= "Input_box">        <Buttonclass= "button"onclick= "Fnlogin ()">Login</Button>    </Div></Div></Body></HTML>
      body {    width:100%;    height:100%;    margin:0;    Background:rgba (20,20,20,20);}

JavaScript Basics, Login verification

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