This is a demonstration calculator implemented in JavaScript.
You must have a JavaScript-capable browser for this to work.
Because we want this calculator to be interactive, both receiving
and processing input, we embed the "calculator"-table
within FORM tags. Each button is specified as an input
source. The FORM tag lacks a METHOD attribute. Normally
this attribute would be required, specifying either POST or
GET, depending on how input is to be passed to an application
through CGI. The FORM tag here also lacks an
ACTION attribute, which would normally tell the browser the
location of the CGI program for processing the form. Since
our form will be processed on the client side, neither of these
attributes is required. Instead our FORM simply has a
NAME attribute, enabling the script to distinguish forms
by name later on. The INPUT tags within this form also differ
from the usual tags. TYPE is specified simply as
"button", which is not one of the normal options.
Also, the INPUT tag contains a new attribute, onClick.
This pair, button and onClick, specifies one means of
passing input to the script. For the "Jcalc" script this
is the only input source used. Because browsers ignore HTML
tags and attributes they do not understand, these new elements will
not cause particular problems with the appearance of the calculator.
Note that the Nselect function, for example, could well be reused
in other applications that require numerical input. The Nselect
function builds up a larger numerical string from individual
number-button clicks.
JScript Calculator
is a Javascript Program -- adapted from a sample calculator Javascript
app from Mark Stone. You can see the JavaScript by using View Source.
©1997 Erik Østergaard, Copenhagen, Denmark.
