learning target
- Master the conditional statement if
- Master the application of prompt()
- Application of alert()
if statement
Syntax 1:
if(condition){
statement1;
}Grammar 2:
if(condition){
statement1;
}else{
statement2;
}Syntax 3:
if(condition){
statement1;
}else if(condition){
statement2;
}...else{
statement3;
}alert()
Syntax: alert()
Function: pop up warning dialog
prompt()
Syntax: prompt()
Function: pop-up input box
return value:
- Click OK to return to the input
- Click cancel, return null
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>警告框elert()和输入框prompt()的用法</title>
</head>
<body>
<script>
var age=prompt("请输入您的年龄"); //()为希望提示用户的标题文字
if(age<18){
alert("您还未成年");
}else{
alert("您已成年,请输入身份证号码");
}
</script>
</body>
</html>
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>警告框elert()和输入框prompt()的用法</title>
</head>
<body>
<script>
var age=prompt("请输入您的年龄"); //()为希望提示用户的标题文字
if(age<18){
alert("您还未成年");
}else if(age>=18 && age<=59){ //18到59岁之间
alert("您可以进入");
}else{
alert("您已超出年龄限制");
}
</script>
</body>
</html>