Powerlog

A logger for Deno that sends your logs wherever you want them.

Getting Started

Firstly,

You need to import the module into your project.

import { Powerlog } from "https://deno.land/x/powerlog/mod.ts";

Secondly,

You should import any built-in transports you want to use.

import {
    WriterTransport,         // For writing to an async writer (an object that has .write).
    StdTransport,            // For writing to stdout or stderr.
    FileTransport,           // For appending to a file.
    TcpTransport,            // For sending logs over a tcp connection or unix sock.
    DiscordWebhookTransport, // For sending discord webhook messages.
} from "https://deno.land/x/powerlog/mod.ts";

Thirdly,

You need a log levels enumerable.

enum MyLogLevels {
    debug,
    info,
    success,
    alert,
    warn,
    critical,
}

Fourthly,

You need to create a new powerlog instance.

const myLogger = Powerlog.get({
    levels: MyLogLevels,
    name: "My Logger"
});

Fifthly,

You can now also create the transports you wish to use.

const myStdoutTransport = new StdTransport({
    levels: MyLogLevels
});

const myFileTransport = new FileTransport({
    levels: MyLogLevels,
    filename: "my.log"
});

Sixthly,

Add the transports to your logger.

await myLogger.use(
    myStdoutTransport,
    myFileTransport
);

Seventhly,

You can now use any of the properties in MyLogLevels as loggging methods.

myLogger.debug("Hello World");

Lastly but not least,

When you’re done with the logger always remember to dispose of its transports.

await myLogger.dispose();

Formatting

When creating transports you will have the ability to add formatting to your messages, however, not all transports have that ability. The WriterTransport object does not have formatting capabilities. It does however have methods <WriterTransport>.dataToByteArray and <WriterTransport>.dataToString. You can extend the WriterTransport and modify those.

Default Formatting

The default formatting applies to FormatTransportBase, FileTransport, StdTransport and TcpTransport.

You can on either of these’s constructors add a formatting property which is a function that returns either a string or a Uint8Array, it can be both synchronous and asynchronous.

Example:

const transport = new StdTransport({
    formatter: data =>
        `[${data.timestamp.toJSON()}] (${data.name}) ${MyLogLevels[data.level]} ${sprintf(data.message, ...data.arguments)}`
});

You can also change the formatter later on with the use <FormatTransportBase>.format(formatter).

Example:

transport.format(
    data =>
        `${MyLogLevels[data.level]} ${sprintf(data.message, ...data.arguments)}`
);

You can also apply a default format on the powerlog instance the same way as above. When adding transports with no formatters to a powerlog instance with a default formatter the powerlog instance will try to apply the default formatter onto the transports on initialization.

Example:

const myLogger = new Powerlog({
    levels: MyLogLevels,
    name: "My Logger",
    formatter: data =>
        `[${data.timestamp.toJSON()}] (${data.name}) ${MyLogLevels[data.level]} ${sprintf(data.message, ...data.arguments)}`
});

You can then also later change the default formatter by using <Powerlog>.format(formatter).

Note that this will not replace the previous default formatters applied to the already existing transports. It will only be applied to new transports.

Example:

myLogger.format(
    data =>
        `${MyLogLevels[data.level]} ${sprintf(data.message, ...data.arguments)}`
);

Discord Formatting

The discord transport uses its own formatter specification. The formatter function is expected to return a discord message object.

import type { IDiscordMessage } from "https://deno.land/x/powerlog/mod.ts";
import { DiscordWebhookTransport } from "https://deno.land/x/powerlog/mod.ts";

Example:

const myDiscordWebhookTransport = new DiscordWebhookTransport({
    levels: MyLogLevels,
    url: "webhook url",
    formatter: data => ({
        content: null,
        embeds: [
            {
                title: MyLogLevels[data.level],
                description: sprintf(data.message, ...data.arguments),
                timestamp: data.timestamp.toJSON()
            }
        ]
    })
});

Again, this can later be changed using <DiscordWebhookTransport>.format(formatter).