javascript - Not seeing why my option will not sum up? -

I am trying to display the options menu of all my options on a product page. I have simplified JSField, as it works.

  & lt; Select name = 'anch1' & gt; & Lt; Option data-value = "" & gt; ---- & lt; / Options & gt; & Lt; Option data-value = "10" & gt; 10++ & lt; / Options & gt; & Lt; Option data-value = "20" & gt; 20++ & lt; / Options & gt; & Lt; Option data-value = "30" & gt; 30++ & lt; / Options & gt; & Lt; Option data-value = "40" & gt; 40++ & lt; / Options & gt; & Lt; Option data-value = "50" & gt; 50++ & lt; / Options & gt; & Lt; / Select & gt; & Lt; Select name = 'ant2' & gt; & Lt; Option data-value = "" & gt; ---- & lt; / Options & gt; & Lt; Option data-value = "10" & gt; 10++ & lt; / Options & gt; & Lt; Option data-value = "20" & gt; 20++ & lt; / Options & gt; & Lt; Option data-value = "30" & gt; 30++ & lt; / Options & gt; & Lt; Option data-value = "40" & gt; 40++ & lt; / Options & gt; & Lt; Option data-value = "50" & gt; 50++ & lt; / Options & gt; & Lt; / Select & gt; & Lt; Select name = 'anch 3' & gt; & Lt; Option data-value = "" & gt; ---- & lt; / Options & gt; & Lt; Option data-value = "10" & gt; 10++ & lt; / Options & gt; & Lt; Option data-value = "20" & gt; 20++ & lt; / Options & gt; & Lt; Option data-value = "30" & gt; 30++ & lt; / Options & gt; & Lt; Option data-value = "40" & gt; 40++ & lt; / Options & gt; & Lt; Option data-value = "50" & gt; 50++ & lt; / Options & gt; & Lt; / Select & gt; $ ('Selection'). Change (work () {var sum = 0; $ ('select: selected'). (Function () {sum + = number ($ (this). Data ('value'));}) $ (" # Sum ") .HTML (sum);});  

But when I add a simplified product select menu, like

the sum does not work correctly, only when I have both newly added menu Selects something happening

The last 2 selection menus do not have data-value set, so add a function (0 + 0 + 0 + NAN + NAN) =" NaN "

"Data-value" set for "new" or "0"

i.e. change

  for the newly added selection & lt; Option & gt; --- & lt; / Option & gt;  

to

  & lt; Option data-value = "" & gt; --- & lt; / Options & gt;  

Just a note ... Both your Bella works in the same way .. Both are the same issue.