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Three ways to use 1.<script></script>:
A. Put in <body>
B. Put in
C. Put in an external JS file
<!DOCTYPE HTML><HTMLLang= "en"><Head> <MetaCharSet= "UTF-8"> <title>Demo</title> <Script> functiondisplaydate () {document.getElementById ("Demo"). InnerHTML=Date (); } </Script> <Scriptsrc= "Yl.js"></Script></Head><Body> <P>Hello</P> <Script>document.write (Date ()) document.getElementById ("Demo"). InnerHTML=Date (); </Script> <Buttontype= "button"onclick=window.alert ("User name must not start with a number")>Press</Button></Body></HTML>
function myFunction () {Document.getelementbyld ("Demo"). Innerhtml= "My first JavaScript function";}2. Three ways of outputting data:
(1). Use the document.write () method to write the contents to an HTML document.
(2). Use the Window.alert () pop-up warning box.
(3). Write to HTML element using InnerHTML.
A. Use the ID property to identify the HTML element.
B. Use the document.getElementById (ID) method to access HTML elements.
C. Use innerHTML to get or insert element content.
<!DOCTYPE HTML><HTMLLang= "en"><Head> <MetaCharSet= "UTF-8"> <title>Demo</title></Head><Body> <PID= "Demo">Hello</P> <Script>document.getElementById ("Demo"). InnerHTML=Date (); </Script> <Buttontype= "button"onclick=window.alert ("User name must not start with a number")>Press</Button></Body></HTML>
3. The login page prepares:
A. Add the error prompt box.
B. Write a good html+css file.
C. Setting the ID of each INPUT element
4. Define JavaScript functions.
A. Verify user name 6-20-bit
B. Verify password 6-20-bit
5.onclick calls this function.
<! DOCTYPE html>
<meta charset= "UTF-8" >
<title> Login </title>
<link rel= "stylesheet" type= "Text/css" href= "C2.css" >
<script>
function Fnlogin () {
var ouname = document.getElementById ("umane");
var oerror = document.getElementById ("Error_box");
var oupass = document.getElementById ("UPass")
if (ouname.value.length<6) {
Oerror.innerhtml= "User name is at least 6 bits"
}
if (ouname.value.length>20) {
Oerror.innerhtml= "User name must not exceed 20 digits"
}
if (ouname.value.length>6&ouname.value.length<20&oupass.value.length<6) {
Oerror.innerhtml= "Password is at least 6 bits"
}
if (ouname.value.length>6&ouname.value.length<20&oupass.value.length>20) {
Oerror.innerhtml= "Password must not exceed 20 digits"
}
}
</script>
<body>
<div class= "BigBox" >
<div class= "box" >
<div class= "Input_box" >
Account: <input id= "umane" type= "text" placeholder= "Please enter user name" >
</div>
<div class= "Input_box" >
Password: <input id= "UPass" type= "password" placeholder= "Please enter password" >
</div>
<div id= "Error_box" ><br></div>
<div class= "Input_box" >
<button onclick= "Fnlogin ()" > Login </button>
<button Onclick=window.alert ("Do you want to cancel the login?" ") > Cancel </button></div>
</div>
</div>
</body>
Align:center; }.bigbox{Display:-webkit-flex;Display:Flex;width:400px;Height:250px;Padding-left:100px;Padding-top:50px;Background-color:Greenyellow; }#input_box{Align:Center;margin:700px;Padding-left:700px; }#error_box{Color:Black; }Body{Padding-right:500px;Margin-top:100px;Padding-left:500px;font-size:16px;Padding-bottom:40px;Padding-top:40px;font-family:Verdana,arial,helvetica,sans-serif; }
JavaScript Basics, Login verification
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