if ((y=="") && (isNaN(parseInt(y))))

[engcomp]

Maybe everybody knows this, but I learned it the hard way: Javascript treats y=="" and y==0 as being the same.

I have a little program that solves nonlinear equations online, see:

http://www.engs-comp.com/solvnonlinearequ/index.html

The evaluation function returns "" if an equation cannot be evaluated for a given x, otherwise, it returns the result of the evaluation, which could be zero (0).

Lo and behold, when it returned 0, it triggered the (y=="&quot test, which stops the program and outputs a message.

I found that you must test:
if ((y=="&quot && (isNaN(parseInt)))

Hope this helps somebody. Regards, Helmt

http://www.engs-comp.com/

 

[trollacious]

Rather than use y=="" here, test for an empty/null string with y.length==0 to see if there's any input at all.