code: function checkDimension(i) {
    const ln = checkNumber(i);
    let li;
  
    if (i >= tokensLength ||
        !ln ||
        i + ln >= tokensLength) return 0;
  
    return (li = checkUnit(i + ln)) ? ln + li : 0;
  }
docs: Check if token is part of a number with dimension unit (e.g. `10px`)
  @param {Number} i Token's index number
  @return {Number}