Button Enable Validation Using Jquery

<script>
    $(document).ready(function() {
        var elems = $('#field1, #field2, #field3');
        elems.on('keyup', function() {
            var hasValue = elems.filter(function() {
                return this.value.length
            }).length != elems.length;
            console.log(hasValue)
            $('#add-fields').prop("disabled", hasValue);
        });
    });
</script>

<!DOCTYPE html>
<html>

<head>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
    <script>
        $(document).ready(function() {
            var elems = $('#field1, #field2, #field3');
            elems.on('keyup', function() {
                var hasValue = elems.filter(function() {
                    return this.value.length
                }).length != elems.length;
                console.log(hasValue)
                $('#add-fields').prop("disabled", hasValue);
            });
        });
    </script>
</head>

<body>
    * All fields must have a value :
    <br />
    <br/> Field 1 :
    <input type="text" id="field1" name="field3" />
    <br>
    <br> Field 2 :
    <input type="text" id="field2" name="field2" />
    <br>
    <br> Field 3 :
    <input type="text" id="field3" name="field3" />
    <br />
    <br />
    <button id="add-fields" disabled>Click</button>
</body>

</html>

Conclusion