src/helper.js
function copyExistingProperties(src, dst) {
  Object.keys(dst).forEach(function(key) {
    if (dst.hasOwnProperty(key) && src.hasOwnProperty(key)) {
      dst[key] = src[key];
    }
  });
}
function copyExistingProperties(src, dst) {
  Object.keys(dst).forEach(function(key) {
    if (dst.hasOwnProperty(key) && src.hasOwnProperty(key)) {
      dst[key] = src[key];
    }
  });
}
function copyExistingProperties ( src , dst ) { Object . keys ( dst ) . forEach ( function ( key ) { if ( dst . hasOwnProperty ( key ) && src . hasOwnProperty ( key ) ) { dst [ key ] = src [ key ] ; } } ) ; }
Copies properties from source to dest only if a matching key is in dest

@param {Object.<string, ?>} src the source
@param {Object.<string, ?>} dst the dest
@private
Copies properties from source to dest only if a matching key is in dest