JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" class="seq" value="" />
<br /><input type="text" class="seq" value="" />
<br /><input type="text" class="seq" value="" />
<br /><input type="text" class="seq" value="" />
<br /><input type="text" class="seq" value="" />
<br /><input type="text" class="seq" value="" />
<br /><input type="text" class="seq" value="" />
<br />
<input type="button" value="Submit" id="submit" />

JavaScript

$(function() {
    $("#submit").click(function() {
        //build a profile of the inputs
        var inputs = [];
        var values = [];
        var dups = false; //track duplicates on pass 1
        
        $(".seq").each(function(i, el) {
            var empty = (el.value == ""); //check if empty
            var exists = (!empty && $.grep(inputs, function(item, index) {
                return (item.Value === el.value);
            }).length > 0); //check if exists
            dups = (dups || exists); //track dups
            
            //add the new input item
            var obj = {
                Element: el,
                Value: el.value,
                Empty: empty,
                Exists: exists
            };
            inputs.push(obj);
            
            //conditionally add the sorting value
            if (!empty && !exists)
                values.push(el.value);
        });
        
        //Validate the inputs. If there are duplicates, don't submit
        $(".seq").css("background-color", "white"); //clear errors
        if (dups) {
            $(inputs).each(function(i, el) {
                if (el.Exists) 
                    el.Element.style.backgroundColor = "red";
            });
        } else {
            values = values.sort();
            alert(values);
        }
    });
});