Expected emission lines from H atom for given series.

expected-emission-lines.js

// Inputs
var presets = {
    lyman: {
        initial: 2,
        final: 1
    },
    balmer: {
        initial: 3,
        final: 2
    },
    paschen: {
        initial: 4,
        final: 3
    },
    brackett: {
        initial: 5,
        final: 4
    },
};

const preset = 'brackett';

var initial = presets[preset].initial;
var final = presets[preset].final;

// Constants
const h = 6.6256e-34;
const c = 3e8;
const R = 1.097e7;

// Formulas
var lambda = 1 / (R * ((1 / (final ** 2)) - (1 / (initial ** 2))));
var E = (h * c) / lambda;

// Outputs
var output = {
    series: preset,
    initial,
    final,
    wavelength: {
        'm': (lambda * 1e7).toPrecision(4) + '*10^-7m',
        'nm': (lambda * 1e7 * 1e2).toPrecision(4) + 'nm',
    },
    energy: {
        'J': (E * 1e18).toPrecision(4) + '*10^-18J',
    },
};
console.log(output);