JSFiddle - React, Tailwind, and code Playground

HTML

<form id="checkinput" action="#">
<input type="text" value="" id="couponcode" name="coupon code name"/>
<input type="button" id="submit" value="Submit"/>
</form>

JavaScript

var arr = [ "CA238", "Pete", 8, "John" ];

$("#submit").click(function(e){
e.preventDefault();
    
    var val=$("#couponcode").val();
    if($.inArray(arr,val)) 
        alert("success");

});