Custom flags

Pass an object to undevice() to add your own flags. Each key becomes a flag name in the result.

Each value can be:

• A function (ua: string) => boolean. It receives the User-Agent trimmed and converted to lowercase.
• An array of strings for case-insensitive substring matching against the User-Agent. The check returns true if at least one substring matches. Special characters such as . and * are treated literally.
• An object with a required detect and an optional exclude. Both fields accept a function or an array of strings. If exclude returns true, the flag is set to false and detect is skipped. Otherwise, the flag takes the result of detect.

A check function:

const { detect } = undevice({
  isCrawler: (ua) => /googlebot/i.test(ua),
});

An array of substrings:

const { detect } = undevice({
  isRawClient: ["curl", "wget"],
});

A check with an array of exclusions:

import { isbot } from "isbot";

const { detect } = undevice({
  isCrawler: {
    detect: isbot,
    exclude: ["curl", "wget"],
  },
});

An array of substrings in detect and a function in exclude:

const { detect } = undevice({
  isCrawler: {
    detect: ["bot", "crawler", "spider"],
    exclude: (ua) => ua.includes("my-health-checker"),
  },
});

Examples with third-party libraries

You can use a function from a third-party library as a check or use its data in your own callback. The examples below use isbot and crawler-user-agents.

isCrawler with isbot

Use isbot to identify bot User-Agents:

npm install isbot

import { isbot } from "isbot";
import { undevice } from "undevice";

const { detect } = undevice({ isCrawler: isbot });
const device = detect({ headers: request.headers });

device.isCrawler; // boolean

isCrawler with crawler-user-agents

You can also build a check from the patterns in crawler-user-agents. Compile the regular expressions once when setting up the detector:

npm install crawler-user-agents

import crawlers from "crawler-user-agents" with { type: "json" };
import { undevice } from "undevice";

const patterns = crawlers.map(({ pattern }) => new RegExp(pattern, "i"));

const { detect } = undevice({
  isCrawler: (ua) => patterns.some((pattern) => pattern.test(ua)),
});

const device = detect({ headers: request.headers });

device.isCrawler; // boolean

Type inference

import { undevice } from "undevice";

const { detect } = undevice({ isRawClient: ["curl", "wget"] });
const device = detect({ userAgent: "curl/8.0" });
device.isRawClient;