Context

Listen to all events

bot.use((context, next) => {
    // ...
});

Listen only to specific events

bot.on("message", (context, next) => {
    // ...
});
// or
bot.on(["message", "callback_query"], (context, next) => {
    // ...
});

You can read API Reference for contexts here.

Context injection

Derive

Derive allows you to inject what's you want to context with access to existing context data and type-safety. A handler will be called every update.

Global derive

import { Bot } from "gramio";

const bot = new Bot(process.env.BOT_TOKEN as string)
    .derive((context) => {
        return {
            key: 1,
        };
    })
    .on("message", (context) => {
        context.key;
    })
    .use((context, next) => {
        context.key;

        return next();
    })
    .on("callback_query", (context) => {
        context.key;
    });

Scoped derive

You can scope the derive to specific update (or updates) with full type support.

import { Bot } from "gramio";

// Simple example
export function findOrRegisterUser(id: number) {
    return {} as Promise<{ id: number; name: string; balance: number }>;
}

const bot = new Bot(process.env.BOT_TOKEN as string)
    .derive(["message", "callback_query"], async (context) => {
        const fromId = context?.from?.id;

        if(!fromId) throw new Error("No from id");

        return {
            fromId,
        }
    })
    .derive("message", async (context) => {
        const user = await findOrRegisterUser(context.fromId);

        return {
            user,
        };
    })
    .on("message", (context) => {
        context.user.
;
Identifier expected.
        //
    })
    .use((context, next) => {
        if (context.is("message")) context.user;

        return next();
    })
    .on("callback_query", (context) => {
        context.user;
Property 'user' does not exist on type 'CallbackQueryContext<Bot<{}, DeriveDefinitions & { message: { fromId: number; }; callback_query: { fromId: number; }; } & { message: { user: { id: number; name: string; balance: number; }; }; }>> & { ...; }'.
        context.fromId
    });

Decorate

With decorate you can inject static values and it will be injected to contexts only when decorate called (so it will not evaluate every update).

import { Bot } from "gramio";

const bot = new Bot(process.env.BOT_TOKEN as string)
    .decorate("TEST", "hi!! you're cute" as const)
    .decorate({
        key: "value",
        key2: "value",
    })
    .use((context) => {
        context.TEST;
        //

        context.k
;
Property 'k' does not exist on type 'Context<Bot<{}, DeriveDefinitions & { global: { TEST: "hi!! you're cute"; }; } & { global: { key: string; key2: string; }; }>> & { TEST: "hi!! you're cute"; } & { ...; }'.
    });