operations with javascript in html document

Question

I want the label with id="risultato" display the area of triangle,I tried to make this,but when I pressed button "risultato:" the risult is NaN,why? Thanks lots

code: https://i.stack.imgur.com/52Pbd.png

Please do not post your code in Image format. Can you please add your code in textual format? — Sayali Sonawane, Sep 27 '16 at 17:16
You should use `base.value` and `altezza.value`. They are input elements, so the `value` fields contains the actual input — eavidan, Sep 27 '16 at 17:16
`value` is missing. `NaN` means its not a number. Since you are not taking value, its not getting integer and hence the error. — Kinshuk Lahiri, Sep 27 '16 at 17:19

score 2 · Accepted Answer · answered Sep 27 '16 at 17:21

You are getting NaN because of this:

var altezza = document.getElementById('altezza');
var base = document.getElementById('base');
(base*altezza/2)

getElementById() does exactly that - gets the element. You just need to get the value from the element e.g. var altezza = document.getElementById('altezza').value;

operations with javascript in html document

1 Answers1