JSFiddle - React, Tailwind, and code Playground

HTML

<input id="Textbox1" type="text" value="A123456,foo,bar,too-looong,B123456,C123456,D123456" />
<button id="validateButton">validate</button>

JavaScript

function validate() {
    var val = document.getElementById("Textbox1").value,
        err = $(val.split(',')).filter(function(){ return this.length != 7; })
                               .toArray();
    if (err.length) {
        alert("All entries must be seven (7) characters in length.  Please correct the following entries: \n" + err);
        return false; 
    }
    return true; 
}
$('#validateButton').click(function() { validate(); });