multiindex_parser.js

function cartesian(arr) {
  return arr.reduce((a, b) =>
    a.map(x => b.map(y => x.concat(y)))
    .reduce((a, b) => a.concat(b), []), [[]]);
}
function parse(f){
	var re = /\[([0-9a-zA-Z,]+[^\]]+)\]/gm;
	var m = null;
	var res = [];
	var lastIndex = 0;
	while(m = re.exec(f)){
 		res.push([f.substring(lastIndex, m.index)]);
 		res.push(m[1].split(",").map(i => "."+i));
 		lastIndex = m.index + m[0].length;
	}
	return cartesian(res).map(r => r.join(""));
}
/**
 * This makes part of a JSON2CSV engine
 * The idea is to simplify the syntax to select fields from complex objects
 * 
 * Given the document
 */
var o = { a:{
     b:['val1'],
     c:[{
       d:1,
       e: 'val2',
       f: 2.3
     }],
     c1:[{
       d:1,
       e: 'val2',
       f: 2.3
     }]
    }
   }
 
parse("a[c,c1][0][e,f]").map(k => [k, eval("o." + k)])

/* OUTPUT
(4) [Array(2), Array(2), Array(2), Array(2)]
0:(2) ["a.c[0].e", "val2"]
1:(2) ["a.c[0].f", 2.3]
2:(2) ["a.c1[0].e", "val2"]
3:(2) ["a.c1[0].f", 2.3]
*/