sendMessage

This page describes the sendMessage() function in zalo-bot-js, used to send a text message to a user or chat through the SDK.

If your bot needs to reply to incoming text, send notifications, or return workflow results, this is one of the most commonly used functions.

Function signature

sendMessage(
  chatId: string,
  text: string,
  options?: SendMessageOptions,
): Promise<Message>

When to use it

• reply to an incoming message
• send proactive notifications to a chat_id
• return results from bot logic or workflows
• send content from webhook, polling, or internal services

Parameters

Parameter	Type	Required	Description
chatId	string	Yes	ID of the target user or chat
text	string	Yes	Text message content (1–2000 characters)
options.reply_to_message_id	string	No	Message ID to reply to
options.parse_mode	ParseMode	No	Enable rich text formatting: "markdown" or "html"
options.text_styles	TextStyleRun[]	No	Direct style runs applied to raw text

Rich text formatting

Bot supports two ways to send formatted messages:

Option 1: parse_mode

Set parse_mode to "markdown" or "html" and write formatted content directly in text. The server parses markup and applies formatting.

Markdown:

await bot.sendMessage(chatId, "**Xin chào** _bạn_, đây là tin nhắn **đậm** và *nghiêng*", {
  parse_mode: "markdown",
});

Supported Markdown syntax:

Syntax	Result
**đậm**, __đậm__	Bold
*nghiêng*, _nghiêng_	Italic
***đậm nghiêng***	Bold + italic
~~gạch~~	Strikethrough
`code`	Monospace
{red}…{/red}	Colored text
{big}…{/big}	Large text

HTML:

await bot.sendMessage(chatId, "<b>Xin chào</b> <i>bạn</i>", {
  parse_mode: "html",
});

Supported HTML tags: <b>, <strong>, <i>, <em>, <u>, <s>, <del>, <h1>–<h6>, <ul>, <ol>, <li>, <p>, <div>, style="...".

Option 2: text_styles

Apply style runs directly to raw text. Each run specifies a range and formatting codes.

await bot.sendMessage(chatId, "Xin chào bạn", {
  text_styles: [
    { start: 0, len: 7, st: ["b", "c_db342e"] }, // bold + red
    { start: 8, len: 4, st: ["i"] },             // italic
  ],
});

Supported style codes (st):

Code	Meaning
b	Bold
i	Italic
u	Underline
s	Strikethrough
f_13, f_15, f_18, f_20	Font size (small / normal / large / x-large)
c_050a19	Default color
c_15a85f	Green
c_f7b503	Yellow
c_f27806	Orange
c_db342e	Red
lst_1	Bullet list
lst_2	Numbered list
ind_1–ind_5	Indentation levels

Priority

If both parse_mode and text_styles are provided, parse_mode takes precedence and text_styles is ignored. They use different coordinate systems and cannot be combined.

Return value

The function returns Promise<Message>.

Minimal example

import { Bot } from "zalo-bot-js";

const bot = new Bot({ token: process.env.ZALO_BOT_TOKEN! });

async function main() {
  const chatId = process.env.ZALO_CHAT_ID!;
  const message = await bot.sendMessage(chatId, "Hello!");
  console.log(message.messageId);
}

void main();

Example with markdown

await bot.sendMessage(chatId, "**Bold** and *italic* text", {
  parse_mode: "markdown",
});

Example with text_styles

await bot.sendMessage(chatId, "Colored text", {
  text_styles: [
    { start: 0, len: 7, st: ["b", "c_f27806"] }, // bold orange
  ],
});

Example in polling

bot.on("text", async (message) => {
  if (!message.text) {
    return;
  }
  await bot.sendMessage(message.chat.id, `You said: ${message.text}`);
});

Example with reply options

bot.on("text", async (message) => {
  await bot.sendMessage(
    message.chat.id,
    "I received your request.",
    {
      reply_to_message_id: message.messageId,
    },
  );
});

Relationship with replyText()

If you already have a Message, you can also use message.replyText(). Internally, that helper calls sendMessage() with the current chat.id.

Practical notes

• sendMessage() is the SDK-level API that developers should call directly
• it returns a parsed Message model instead of exposing raw transport results
• text length must be between 1 and 2000 characters
• parse_mode and text_styles are mutually exclusive; parse_mode wins if both are set

Next

• See replyText for the message helper version.
• See sendPhoto if you want to send images instead of plain text.

Last updated: September 7, 2026