function defaults(dst, src) {
  forEach(src, function(value, key) {
    if (!isDefined(dst[key])) {
      dst[key] = value;
    }
  });
}
function defaults(dst, src) {
  forEach(src, function(value, key) {
    if (!isDefined(dst[key])) {
      dst[key] = value;
    }
  });
}
function defaults ( dst , src ) { forEach ( src , function ( value , key ) { if ( ! isDefined ( dst [ key ] ) ) { dst [ key ] = value ; } } ) ; }
shallow copy over values from `src` that are not already specified on `dst`
shallow copy over values from src that are not already specified on dst