MessageHandler

This page describes MessageHandler in zalo-bot-js, a handler used to process updates based on filters.

This is the right choice when you want to handle updates by content type such as text, photo, or sticker in the Application flow.

How it works

MessageHandler receives:

• a filter
• a callback

The handler runs when:

• update.message exists
• filter(update) returns true

Example

import "dotenv/config";
import { ApplicationBuilder, MessageHandler, filters } from "zalo-bot-js";

const app = new ApplicationBuilder()
  .token(process.env.ZALO_BOT_TOKEN!)
  .build();

app.addHandler(new MessageHandler(filters.TEXT, async (update) => {
  await update.message?.replyText("I received a text message.");
}));

void app.runPolling();

Next

• See filters for the built-in filters.
• See Application to understand handler dispatching.

Last updated: April 5, 2026