send-file-message.js

// Create a `FileMessageParams` object.
const params = new sb.FileMessageParams();
params.file = FILE;
params.parentMessageId = PARENT_MESSAGE_ID; // This specifies the unique ID of a parent message which has a thread of replies. If the message sent through the `sendUserMessage()` method is a parent message, the value of this property is 0.
...

// Pass the params to the parameter in the `sendFileMessage()` method.
groupChannel.sendFileMessage(params, (message, error) => {
    if (error) {
        // Handle error.
    }

    // A reply to a specific message in the form of a file message is successfully sent.
    ...
});