how to check a valid domain name and username with regular expression in javascript?

-<script>
function validate()
{
 var patt1=new RegExp(/^[a-zA-Z0-9._-]+\\[a-zA-Z0-9.-]$/);

   var text= document.getElementById('text1').value;

  alert(patt1.test(text));

}

but it does not work for me.

Use this:

<script>
    function frmValidate() {
        var val = document.frmDomin.name.value;
        if (/^[a-zA-Z0-9][a-zA-Z0-9-]{1,61}[a-zA-Z0-9](?:\.[a-zA-Z]{2,})+$/.test(val)) {
            alert("Valid Domain Name");
            return true;
        } else {
            alert("Enter Valid Domain Name");
            val.name.focus();
            return false;
        }
    }
</script>

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