JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" id="checkbox" name="checkbox">
<input type="checkbox" id="checkbox" name="checkbox">
<input type="submit" value="Send" id="testcheck" />

JavaScript

$("#testcheck").on('click', function() {
    if (jQuery("#checkbox").is(":checked")) {
        alert("first button checked");
    }
    else {
        alert("none checked");
    }
});