Summary js-emass is a JavaScript module that quickly and accurately calculates the isotopic
envelope of a molecule. Isotopic envelopes are commonly encountered in the field of mass
spectrometry which identifies molecules by their mass fingerprint. A mass spectrum is
generated by measuring many copies of a molecule. The natural variations of isotopes then
leads to a splitting of the signal. Instead of measuring a single mass, the instrument
measures multiple masses which are then dubbed the isotopic envelope. The intended …