Addition returns wrong value in JavaScript

Question

When I tried with additions of variables I saw that:

I think it's because this doesn't contain an integer.

  var month = $("#monthd").val();
  var J = 1;
  var D = 8;
  var K = J + D;
  var U = J + month;

As you can see in fiddle J + month returns 110 instead of 11, why?

`.val()` returns a string. Convert to a number with `var month = Number($("#monthd").val());` or with the unary plus operator: `var month = +$("#monthd").val();`. — nnnnnn, Aug 20 '16 at 10:54
Possible duplicate of [How do I convert a string into an integer in JavaScript?](http://stackoverflow.com/questions/1133770/how-do-i-convert-a-string-into-an-integer-in-javascript) — JJJ, Aug 20 '16 at 11:01

score 1 · Accepted Answer · answered Aug 20 '16 at 11:22

its a string, so the number you are adding gets coerced into a string as well. "10" + "1" = "101";

simply wrap the value returned in a Number Construct

var month = Number($("#monthd").val());

additionally you can use parseInt if the values are integers.

var month = parseInt($("#monthd").val(), 10);

the , 10 is important to parse it with base 10.

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