geojson.js
function addExtra(properties, extra) {
    for(var key in extra){
      if(extra.hasOwnProperty(key)) {
        properties[key] = extra[key];
      }
    }

    return properties;
  }
function addExtra(properties, extra) {
    for(var key in extra){
      if(extra.hasOwnProperty(key)) {
        properties[key] = extra[key];
      }
    }

    return properties;
  }
function addExtra ( properties , extra ) { for ( var key in extra ) { if ( extra . hasOwnProperty ( key ) ) { properties [ key ] = extra [ key ] ; } } return properties ; }
Adds data contained in the `extra` parameter if it has been specified
Adds data contained in the extra parameter if it has been specified