Parses a Javascript data structure (e.g the content of a mongodb collection) and infers a schema definition

map_datastructure.js

/**
 * Map_schema.js
 * 
 * Parses a Javascript data structure (e.g the content of a mongodb collection) 
 * and populates a schema definition with its attribute names and types. 
 *
 */

function typeOf(value) {
    var s = typeof value;
    if (s === 'object') {
        if (value) {
            if (value instanceof Array) {
                s = 'array';
            }
        } else {
            s = 'null';
        }
    }
    return s;
}

var db=[
  {'a': 33, 'b': {  
     'bb' : 44,
     'bc' : {
        'bcc': null
     },
    'bd' : null,
    'be' : true,
    'bf' : false
  },
   'c': null
  },
  {'x':{'bf':false,'xx':22}},
  {'y':[2,3,4,5]},
  {'z': {'za':[1,3,4,{'zaa':22}]}}
]

schema={};

var parse_struct=function(obj,parents){
  var parents=(parents) ? parents : []; 

  print('-----------------------------');
  print('receiving:'+parents.join('.'));

  var child_attr_count=0;
  var attr_count = 0;
  for (attr in obj) attr_count++; 
  

  var i=attr_count;
  for (attr in obj) { 

        print('i='+i); 

        var child_attr_count=0;
        //count attributes in child attribute
        for(child_attr in obj[attr]) child_attr_count++;     
   
        var separator=(parents.length > 0) ? '.' : '';
        var path=parents.join('.')+separator+attr;
          
        if (!schema[path] && isNaN(parseInt(attr))) {
           print(attr+'=>'+child_attr_count);
           schema[path] = typeOf(obj[attr]);
        }
        // add to parents if child attribute exists and 
        // it is not a numeric key
        if (child_attr_count > 0 && isNaN(parseInt(attr))) {
           parents.push(attr);
        } 

        //remove parent when no sibling elements exist (i.e. i==1)
        if (parents.length > 0 && i == 1 && child_attr_count == 0) {
          var p= parents.pop()
          print('popping '+p);
        }
     
     i--;
     print('sending:'+parents.join(''))
     parse_struct(obj[attr],parents);
  }
}


print(db.toSource());
parse_struct(db,[]);
print(schema.toSource());


//output
//{'a:"number", b:"object", 'b.bb':"number", 'b.bc':"object", 'b.bc.bcc':"null", 'b.bd':"null", 'b.be':"boolean", 'b.bf':"boolean", c:"null", x:"object", 'x.bf':"boolean", 'x.xx':"number", y:"array", z:"object", 'z.za':"array", 'z.za.zaa':"number"}