consonance/index.js

Fix your typographic scale

const R = require('ramda');
const ms = require('simple-modular-scale');

const consonance = (() => {
  "use strict";

  const mapIndexed = R.addIndex(R.map);

  const comparator = R.curry((a, b) => a - b);

  const toScale = R.curry((scale, input, i) => {
    const difference = R.pipe(comparator(input), Math.abs);

    let reducer = (memo, val) => {
      var d0 = difference(memo);
      var d1 = difference(val);
      return d1 < d0 ? val : memo;
    };

    let output = R.reduce(reducer, Infinity, scale);

    return { input, output, i };
  });

  const consonance = (sizes, options = {}) => {
    var scale;

    if (R.isArrayLike(options)) {
      scale = options;
    } else {
      scale = ms(options);
    }

    const sortedScale = R.sort(comparator, scale)

    let fn = toScale(sortedScale);

    return mapIndexed(fn, sizes);
  };

  return consonance;
})();

if (typeof module != "undefined" && module.exports)
  module.exports = consonance;