cexio.js
function(to_clean) {
    _.map(to_clean, function(value, key, to_clean) {
      if (value === undefined) {
        delete to_clean[key];
      }
    });
    return to_clean;
  }
function(to_clean) {
    _.map(to_clean, function(value, key, to_clean) {
      if (value === undefined) {
        delete to_clean[key];
      }
    });
    return to_clean;
  }
function ( to_clean ) { _ . map ( to_clean , function ( value , key , to_clean ) { if ( value === undefined ) { delete to_clean [ key ] ; } } ) ; return to_clean ; }
compact for objects
compact for objects