CallbackContext

This page describes CallbackContext in zalo-bot-js, the context object passed to the callbacks of CommandHandler and MessageHandler.

CallbackContext helps callbacks quickly access application, bot and the list of args already separated from the command.

Key properties

• application
• bot
• args

Example with CommandHandler

app.addHandler(new CommandHandler("start", async (update, ctx) => {
  console.log(ctx.args);
  await ctx.bot.sendMessage(update.message!.chat.id, "Xin chào!");
}));

How args works

For example if the user submits:

/start demo value

then ctx.args would be:

["demo", "value"]

When should you use it?

• callback needs to be reused bot
• callback needs to access application
• The command callback needs to read the parameters after the command

Next

• See CommandHandler to see when CallbackContext is transmitted.
• See Application to understand the relationship between context and app.

Last updated: April 5, 2026