JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="txtemail"/>
<input type='button' id='btnvalidate' onclick='javascript:ValidateData();' value='validate' />

JavaScript

function ValidateData(){    
var email = $('#txtemail').val();
if(email=="")
{
    alert("Enter emailid");
    $("#txtemail").focus();
    return false;
}

else if(email!="")
{
    var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;

    if (!filter.test(email)) 
    {   
        //alert(email)
        //alert(filter.test(email.value)) 
        alert('Please provide a valid email address');
        email.focus();
        return false;
    }
}
}