вкач

var request = require( "request" );

// access token
var token = "";

// ид конфы
var chatid = "";

request(
{
    url: "https://api.vk.com/method/messages.getChatUsers",
    qs:
    {
        access_token: token,
        chat_id: chatid,
        fields: "",
        v: "5.131"
    }
}, function( error, response, body )
{
    if( error )
    {
        console.log( "!! ERROR !!" );
        console.log( error );
    }
    else
    {
        var parse = JSON.parse( body ).response;

        console.log( "\n\n\n" );

        var str = "";

        for( var i = 0; i < parse.length; i++ )
        {
            var id = parse[ i ];
            if( id > 0 )
            {
                str += "@id" + id;

                if( i != ( parse.length - 1 ) )
                    str += " ";
            }
        }

        console.log( str + "\n\n\n" );
    }
} );