JSFiddle - React, Tailwind, and code Playground

by nnnnnn

HTML

<form id="form1" name="form1">
<input type="checkbox" name = "checkbox-1[]" class="checkbox" value ="1" />

<input id="test" type="button" value="Test" />
</form>

JavaScript

document.getElementById("test").onclick = function() {
    isCountCheck("Check something");
};

function isCountCheck(helperMsg) {
    var i, dLen = document.form1["checkbox-1[]"].length;
    if (typeof dLen === "undefined") {
        if (document.form1["checkbox-1[]"].checked) return true;
    }
    else {
        for (i = 0; i < dLen; i++) {
            if (document.form1["checkbox-1[]"][i].checked) return true;
        }
    }
    alert(helperMsg);
    return false;
}