JSFiddle - React, Tailwind, and code Playground

HTML

<form>
<div><input class="required"></div>
<div><input></div>
<div><input class="required"></div>
<div><input></div>
<input type="submit">
</form>

CSS

.required {
    border: 1px solid #0000ff;
}

.highlight {
    border-color: #ff0000;
}

JavaScript

$("form").submit(function() {
    var isFormValid = $(".required").removeClass("highlight").filter(function() {
        return $.trim(this.value) == "";
    }).addClass("highlight").length == 0;

    if (!isFormValid) {
        alert("Please fill in all the required fields (indicated by *)");
    }
    return isFormValid;
});