Simple query language parser in PEGjs

output.json

{
   "type": "OR",
   "terms": [
      {
         "type": "AND",
         "terms": [
            "foo",
            "bar"
         ]
      },
      {
         "type": "AND",
         "terms": [
            "baz",
            {
               "type": "OR",
               "terms": [
                  "foo2",
                  "foo3",
                  {
                     "type": "AND",
                     "terms": [
                        "baz1",
                        "baz2"
                     ]
                  }
               ]
            }
         ]
      }
   ]
}

query.peg

{
  function makeNode(type, head, tail) {
    return tail.length > 0
      ? {
          type:  type,
          terms: [head].concat(tail.map(function(t) { return t[1]; }))
        }
      : head;
  }
}

OrExpression 
  = head:AndExpression tail:(OR AndExpression)* { return makeNode("OR", head, tail); }

AndExpression 
  = head:primary tail:(AND? primary)* { return makeNode("AND", head, tail); }

primary 
  = Word
  / GROUP_START OrExpression:OrExpression GROUP_END { return OrExpression; }

Word 
  = !OR !AND !GROUP_START !GROUP_END chars:[^ \r\n\t,\(\)]+ _ { return chars.join(""); }

OR  
  = "OR"  _
  / "," _

AND 
  = "AND" _

GROUP_START 
  = _ "(" _

GROUP_END 
  = _ ")" _

_ 
  = [ \r\n\t]*

sample-query.txt

foo bar, baz (foo2, foo3, (baz1 baz2))