How to display a digital (numerical) value from a checkbox using js?

Question

PHP

I have the most banal checkbox, I need that when I click on this square, I would display the tittle value of this checkbox in a certain place (there is a tag <p>with id = "result"), that is, I marked the checkbox, the amount increased for example by 100r.
I tried it, it gives me the Nan value.

<div class="kadzakad" action="" method="post">
<input title="53" onchange="calc()" type="radio" name="kad_1" id="kad_1">
  <label class="kad" for="kad_1"><b>Внутри КАД/</b></label>
</div>

function calc() {           
    var ter = document.getElementById("kad_1").checked;
    var result = document.getElementById("result");
    var price = 100;

    price =parseInt(ter.title);

    result.innerHTML = price;
}

Answer 1

var ter = document.getElementById("kad_1").checked; //true или false
price =parseInt(ter.title); //  parseInt(undefined)

Were you crazy?

var ter = document.getElementById("kad_1"),
      price = parseInt(ter.title); //А лучше просто +ter.title

Mini code rewrite

function calc() {
  var result = document.getElementById("result");
  //this и так document.getElementById("kad_1");              
  
  result.innerHTML = +this.title;
}

Answer 2

NaN is not a number. Most likely you are not getting a number somewhere.
You can get the title value like this:

$("#kad_1").click(function() {
    // получаем значение title
    var title = $(this).attr("title");

     // вставляем данные в result
    $("#result").html(title);
});

If you need to increase the number in result, then:

var result = +("#result").html() + title;
 $("#result").html(result);

But in this case, if the user unchecks the checkbox, will the final cost need to be reduced? Then use checked.