PEG.js syntax for parising ingredient line of recipe

ingredient.pegjs

start
  = lines

lines
  = line+

line
  = val:ingredientLine "/n"? { return val }

ingredientLine
  = amt:quantity " " unt:unit " " ing:words {
    return { amount:amt, unit:unt, ingredient:ing };
  }

quantity
  = compoundFraction
  / part:fraction { return [0].concat(part) }
  / wholeAmt

integer
  = digits:[0-9]+ { return parseInt(digits.join(""), 10); }

wholeAmt
  = amt:integer { return [amt] }

fraction
  = num:integer "/" den:integer { return [num, den]; }

compoundFraction
  = whole:wholeAmt " " part:fraction { return whole.concat(part); }


cup = "cups"/"cup"                 { return "cup" }
tsp = "teaspoon"/"teaspoons"/"tsp" { return "tsp" }

unit
  = cup
  / tsp

word
  = letters:[a-z]i+ { return letters.join(""); }

words
 = left:word " " right:words { return [left].concat(right).join(" "); }
 / left:word " " right:word { return [left, right].join(" ") }