Nothing to see here, this toolbox is running in the console. Try for example:
Na + Cl
> 58.439769282
H*2 + O
> 18.015
C*6 + H*12 + O*6
> 180.156
H*2 + S + O*4
> 98.072
You can also try it with molecules, using the periodic table's eval method:
pt.eval('H2SO4')
> 98.072
pt.eval will also recognize multiplier prefixes as one will often find in reaction formulas with
pt.eval('2H2SO4')
> 196.144
pt.eval('C9H8O4')
> 180.159
pt.eval('pt.eval('CH3COOC6H4COOH')')
> 180.159
pt.eval('pt.eval('CH3COOC6H4COOH')')
> 180.159
pt.eval('Ca(OH)2')
> 74.0924