code: function checkProperty(i) {
    const start = i;
    let l;
  
    if (i >= tokensLength) return 0;
  
    if (l = checkVariable(i) || checkIdent(i)) i += l;
    else return 0;
  
    return i - start;
  }
docs: Check if token is part of a property
  @param {Number} i Token's index number
  @returns {Number} Length of the property