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JavaScript Basics, Login front-end verification

Source: Internet
Author: User
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    1. Three ways to use <script></script>:
      1. Put in the <body>
      2. Put in the
      3. Placed in an external JS file
    2. Three ways to output data:
      1. Use the document.write () method to write content to an HTML document.
      2. Use the Window.alert () pop-up warning box.
      3. Writes to an HTML element using InnerHTML.
        1. Use the ID property to identify the HTML element.
        2. Use the document.getElementById (ID) method to access HTML elements.
        3. Use innerHTML to get or insert element content.

    3. 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
    4. Defines a JavaScript function.
      1. Verify user name 6-20-bit
      2. Verify password 6-20-bit
    5. The onclick invokes this function.

<!DOCTYPE HTML><HTMLLang= "en"><Head>    <MetaCharSet= "UTF-8">    <title>Title</title></Head><Body>    <P>Hello</P>    <Script>document.write (Date ())</Script><Buttontype= "button"onclick=window.alert ("User name cannot start with a number")>Login</Button></Body></HTML>

<!DOCTYPE HTML><HTMLLang= "en"><Head>    <MetaCharSet= "UTF-8">    <title>Login</title>    <Linkrel= "stylesheet"type= "Text/css"href=".. /static/css/1111.css ">    <Script>         functionMyLogin () {varOuname=document.getElementById ("name")        varOerror=document.getElementById ("Error_box")        varOpassword=document.getElementById ("Password")         if(OUname.value.length<6||OUname.value.length> -) {Oerror.innertext="user name must be 6-20-bit"; return; }            Else if(Opassword.value.length<6||Opassword.value.length> -) {Oerror.innertext="Password must be 6-20-bit"; return; }            Else{oerror.innerhtml=""; }             }    </Script></Head><Body><Divclass= "AA" >    <Divclass= "Login" ><H2>Login</H2></Div>    <Divclass= "Aa1" >Name:<inputID= "Name"type= "text"placeholder= "Please enter user name"><BR>Password:<inputID= "Password"type= "Password"placeholder= "Please enter password"><BR>        </Div>        <DivID= "Error_box"><BR></Div>      <Divclass= "Aa2" >         <Buttononclick= "MyLogin ()">Login</Button>         <Buttontype= "button"onclick=window.alert ("Whether to cancel login! ")>Cancel</Button>    </Div></Body></HTML>

Css:

Div{margin:0 Auto;text-align:Center;Backgroup-color:Gray;}. AA{width:350px;Height:200px;Background-color:Black;Margin-top:100px;}. Login{font-size:25px;Color:Cyan;}. Aa1{font-size:16px;Font-weight:Bold;Color:Cyan; }. Aa2{width:100px;Height:30px;Boder-style:Hidden;}. Design{font-size:10px;Color:Cyan;}#error_box{Color:Cyan;}

JavaScript Basics, Login front-end verification

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