button group get value

<div class="btn-group" data-toggle="buttons-radio">
        <button class="btn">1</button>
        <button class="btn">2</button>
        <button class="btn">3</button>
        <button class="btn">4</button>
</div>




var num = null;
var ele = document.querySelectorAll(".btn-group > button.btn");
for(var i=0; i<ele.length; i++){
    ele[i].addEventListener("click", function(){
        num = +this.innerHTML;
        alert("Value is " + num);
    });
}
Or jQuery:

var num = null;
$(".btn-group > button.btn").on("click", function(){
    num = +this.innerHTML;
    alert("Value is " + num);
});