how to make a warning to the user when the data entered is not appropriate? when a user is entering his data, an alert will appear when entering data that is not appropriate. For example, in the input field, the username must only use the alphabet and numbers and may not use symbols. If the user enters a symbol, an alert will appear. example :
function validation() {
let nameregex = /^[a-zA-Z]+$/;
let emailregex = /^[a-zA-Z0-9]+@(gmail|yahoo|outlook)\.com$/;
let userregex = /^[a-zA-Z0-9]{5,};
if (!nameregex.test(name.value)) {
alert("Nama harus menggunakan alfabet");
return false;
}
if (!emailregex.test(email.value)) {
alert("Masukan email yang valid");
return false;
}
if (!user.test(username.value)) {
alert("username bisa menggunakan alphabet\n-username menggunakan 5 karakter\n ");
return false;
}
return true;
}
Here is a minimalist example of how you can do it. In this case there is no JavaScript required:
<form>
<input type="text" name="name" required pattern="[a-zA-Z]+" title="letters only, at least one character" placeholder="Name"><br>
<input type="text" name="name" required pattern="^[a-zA-Z][a-zA-Z._]*@(gmail|yahoo|outlook)\.com$" title="Only email accounts from Gmail, Yahoo or Microsoft are admissible." placeholder="email"><br>
<input type="text" name="uname" required pattern="[a-zA-Z0-9]{5,}" title="Letters and numbers only, at least five characters are required." placeholder="username">
<button>OK</button>
</form>