javascript - How to get sum of the calculated column on input -

i have tree number columns, , create calculated column sum of tree inputs , have click save see change . i'm looking result on calculated column ,when type or change number in 1 of 3 column before pressing save. tried javascript code :

function myfunction() {     var x = document.getelementbyid("myinput").value;     document.getelementbyid("demo").innerhtml = "you wrote: " + x; } 

but in case have 3 number columns idea?

see solution below. you'll have add validation numbers allowed

var inputs = document.getelementsbyclassname("myinput");    function myfunction() {  	var total = 0;        array.prototype.foreach.call(inputs, function (input) {          total += +input.value;      });        document.getelementsbyclassname("myoutput")[0].innerhtml = "the total is: " + total;  }    (var = 0; < inputs.length; i++) {      inputs[i].addeventlistener("input", function () {          myfunction();      });  }

<form action="#">      <input type="text" class="myinput">      <input type="text" class="myinput">      <input type="text" class="myinput">  </form>    <div class="myoutput"></div>

what loop through inputs while attaching event listener , calculating total. there 2 ways this, both implemented above.