Tree Parsing with Peg.js

treeparsing.js

var PEG = require('pegjs');

var parser = PEG.buildParser(`
tree = fork?
fork = name:[a-z] c:children? { return Object.assign({name}, c); }
children = '(' left:tree ',' right:tree ')' {return {left,right}}
`);

var tree = parser.parse('a(b,c(,d))');
console.log(tree);

function treeToString(tree) {
  if (tree) {
    if (tree.left || tree.right)
      return tree.name + '(' + treeToString(tree.left) + ',' + treeToString(tree.right) + ')'
    else
      return tree.name;
  } else {
    return "";
  }
}
console.log(treeToString(tree));

https://wiki.haskell.org/99_questions/61_to_69#Problem_67A