code: function frequencies(sequence) {
    const index = {};
  
    // Handling strings
    sequence = seq(sequence);
  
    for (let i = 0, l = sequence.length; i < l; i++) {
      const element = sequence[i];
  
      if (!index[element])
        index[element] = 0;
      index[element]++;
    }
  
    return index;
  }
docs: Function taking a sequence and computing its frequencies.
  
  @param  {mixed}  sequence - The sequence to process.
  @return {object}          - A dict of the sequence's frequencies.
  
  @example
  // frequencies([1, 1, 2, 3, 3, 3]) => {1: 2, 2: 1, 3: 3}
  // frequencies('test') => {t: 2, e: 1, s: 1}