index.js

module.exports = filterObjectOnSchema;

function filterObjectOnSchema(schema, doc) {

  var results;

  //console.log("DOC: ", JSON.stringify(doc, null, 2));
  //console.log("SCH: ", JSON.stringify(schema, null, 2));

  if(schema.type === 'object') {
    results = {}; // holds this levels items

    // process properties  -  recursive
    Object.keys(schema.properties).forEach(function(key) {
      if(typeof(doc[key]) !== 'undefined') {
        if(doc[key] === null) {
          results[key] = doc[key];
        } else {
          var sp = schema.properties[key];
          if(sp.type === 'object') {

            // check if property-less object (free-form)
            if(sp.hasOwnProperty('properties')) {
              results[key] = filterObjectOnSchema(sp, doc[key]);
            } else {
              if(Object.keys(doc[key]).length > 0) {
                results[key] = doc[key];
              }
            }
          } else if(sp.type === 'array') {
            if(doc[key]) results[key] = filterObjectOnSchema(sp, doc[key]);
          } else if(sp.type === 'boolean' || sp.type === 'number' || sp.type === 'integer' || sp.type === 'string') {
            if(typeof doc[key] !== 'undefined') results[key] = doc[key];
          } else {
            if(doc[key]) results[key] = doc[key];
          }
        }
      }
    });

  } else if(schema.type === 'array') {
    // arrays can hold objects or literals
    if(schema.items.type === 'object') {
      results = [];
      doc.forEach(function(item) {
        results.push(filterObjectOnSchema(schema.items, item));
      });
    } else {
      results = doc;
    }
  }

  return results;
}