Better Auth

The Authentication Library for Javascript.

Installation

pnpm install better-auth

Usage

Start by create a folder called auth in your project somewhere.

Create two files server.ts and client.ts in the auth folder.

In the server.ts file, create a betterAuth instance.See the example below.

import { betterAuth } from 'better-auth';
import { prismaAdapter } from "better-auth/adapters/prisma-adapter"
import { github } from "better-auth/providers"

export const auth = betterAuth({
    //database adapter
    adapter: prismaAdapter(prisma),
    //auth providers
    providers: [github({
        clientId: "",
        clientSecret: ""
    })],
   /**
    * better auth requires you to define a user schema.
    * The only field assumed to be present is the id 
    * field.
    */
    user: {
        fields: {
            email: {
                type: "string"
            },
            emailVerified: {
                type: "boolean"
            },
            name: {
                type: "string"
            },
            image: {
                type: "string"
            }
        }
    }
})

Now you need to mount the handler on your application.

Next JS

app/api/[...auth]/routes.ts

import { handler } from "@/lib/auth/server";
import { toNextJSHandler } from "better-auth/next";

export const { GET, POST } = toNextJSHandler(handler);

SvelteKit

src/hooks.server.ts

import { auth } from "$lib/auth/server";
import { svelteKitHandler } from "better-auth/svelte-kit";

export async function handle({ event, resolve }) {
	return svelteKitHandler({ auth, event, resolve });
}

1. In the client.ts file, create a client betterAuth instance. See the example below.

Make sure to import the auth instance from the server.ts file as a type and pass it to the createAuthClient function. That will be used to infer from your auth config on the server.

import { createAuthClient } from "better-auth/client"
import type { auth } from "./server"

export const client = createAuthClient<typeof auth>()({
    baseURL: "http://localhost:3000" //the base url of the server
})

5. Now you can use the client instance to authenticate users in your client side code. See the example below.

import { client } from "@lib/auth/client"

const loginWithGithub = async () => {
    const user = await client.signInOrSignUp({
        provider: "github",
        //this data will be used to create a user if the user does not exist
        data: {
            email: "email" //this is mapping the field to the response from the provider
            name: "name",
            image: "avatar_url",
            emailVerified: {
                value: true //you can pass a static value like this
            }
        },
        callbackUrl: "http://localhost:3000/dashboard" //the url to redirect to after authentication. This is optional.
    })
}