Scales in javascript - d3 inspired

scales.js

'use strict';

module.exports = (function() {
  var linear = function(domain, range) {
    var d0 = domain[0], r0 = range[0], multipler = ( range[1] - r0 ) / ( domain[1] - d0 );

    return function ( num ) {
      return r0 + ( ( num - d0 ) * multipler );
    };
  }

  var log = function(domain, range, base) {
    var rBase = base || 10;

    function logVal(v) {
      if(v === 0) {
        return 0;
      } else {
        return Math.log(v) / Math.log(rBase);
      }
    }
    var linearScale = linear([logVal(domain[0]), logVal(domain[1])], range);

    return function(num) {
      return linearScale(logVal(num));
    };

  }

  return {
    linear: linear,
    log: log
  };
})();