FastOG
Topik

Pembuatan Gambar OG untuk Aplikasi React

Buat og:image dengan React menggunakan API FastOG — dengan langganan API Dinamis (buat kunci API Anda di dasbor), berbasis langganan, diamankan dengan HMAC. Panduan ini menunjukkan cara membuat utilitas penanda tangan (signer) untuk URL gambar OG yang ditandatangani HMAC dan merender gambar Open Graph dinamis secara langsung. Coba Penguji Gambar OG Gratis untuk melihat pratinjau desain Anda sebelum dirilis.

Memulai dengan Cepat

1. Buat utilitas penanda tangan (signer)

javascript
// src/utils/og-image-signer.js
export async function generateSignedOgUrl(params, options = {}) {
    const {
        baseUrl = "https://fastog.com/api/v1/og",
        apiKey = import.meta.env.VITE_FASTOG_API_KEY ||
            process.env.REACT_APP_FASTOG_API_KEY,
        hmacSecret = import.meta.env.VITE_FASTOG_HMAC_SECRET ||
            process.env.REACT_APP_FASTOG_HMAC_SECRET,
    } = options;

    if (!apiKey || !hmacSecret) {
        throw new Error("Missing FASTOG_API_KEY or FASTOG_HMAC_SECRET");
    }

    // RFC-3986 percent-encoding: keep A-Za-z0-9-._~
    const enc = (s) =>
        encodeURIComponent(s).replace(
            /[!'()*]/g,
            (c) => "%" + c.charCodeAt(0).toString(16).toUpperCase(),
        );

    // Every query param except the signature, INCLUDING key
    const all = { ...params, key: apiKey };

    // Canonical query: sorted enc(key)=enc(value) pairs joined with &
    const pairs = [];
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            pairs.push(`${enc(k)}=${enc(vv)}`);
        }
    }
    pairs.sort();
    const canonical = pairs.join("&");

    // Sign the exact bytes the server will verify (Web Crypto HMAC-SHA256)
    const signingKey = await crypto.subtle.importKey(
        "raw",
        new TextEncoder().encode(hmacSecret),
        { name: "HMAC", hash: "SHA-256" },
        false,
        ["sign"],
    );
    const signature = Array.from(
        new Uint8Array(
            await crypto.subtle.sign(
                "HMAC",
                signingKey,
                new TextEncoder().encode(`GET/api/v1/og\n${canonical}`),
            ),
        ),
    )
        .map((b) => b.toString(16).padStart(2, "0"))
        .join("");

    // Build the URL from the same pairs so bytes match the canonical form
    const url = new URL(baseUrl);
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            url.searchParams.append(Array.isArray(v) ? `${k}[]` : k, vv);
        }
    }
    url.searchParams.set("s", signature);

    return url.toString();
}

⚠️ Penting: Dalam SPA React, penandatanganan terjadi di sisi klien. Untuk produksi, pindahkan penandatanganan ke rute API backend agar rahasia HMAC tetap aman.

Backend Express

javascript
// server/routes/og.js
import express from "express";
import crypto from "crypto";

const router = express.Router();

router.get("/api/og", (req, res) => {
    const { title, template = "default", ...params } = req.query;

    if (!title) {
        return res.status(400).json({ error: "Missing title" });
    }

    const apiKey = process.env.FASTOG_API_KEY;
    const hmacSecret = process.env.FASTOG_HMAC_SECRET;

    const enc = (s) =>
        encodeURIComponent(s).replace(
            /[!'()*]/g,
            (c) => "%" + c.charCodeAt(0).toString(16).toUpperCase(),
        );

    const all = { template, title, ...params, key: apiKey };

    const pairs = [];
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            pairs.push(`${enc(k)}=${enc(vv)}`);
        }
    }
    pairs.sort();
    const canonical = pairs.join("&");

    const signature = crypto
        .createHmac("sha256", hmacSecret)
        .update(`GET/api/v1/og\n${canonical}`)
        .digest("hex");

    const url = new URL("https://fastog.com/api/v1/og");
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            url.searchParams.append(Array.isArray(v) ? `${k}[]` : k, vv);
        }
    }
    url.searchParams.set("s", signature);

    res.json({ ogImageUrl: url.toString() });
});

export default router;

Komponen React

jsx
// src/components/OgImage.jsx
import { useState, useEffect } from "react";

export function useOgImage(params) {
    const [ogImageUrl, setOgImageUrl] = useState(null);

    useEffect(() => {
        const searchParams = new URLSearchParams(params);
        fetch(`/api/og?${searchParams}`)
            .then((res) => res.json())
            .then((data) => setOgImageUrl(data.ogImageUrl))
            .catch((err) => console.error("Failed to generate OG image:", err));
    }, [JSON.stringify(params)]);

    return ogImageUrl;
}

Contoh Posting Blog

jsx
// src/pages/BlogPost.jsx
import { useEffect, useState } from "react";
import { useOgImage } from "../components/OgImage";

export default function BlogPost({ post }) {
    const ogImageUrl = useOgImage({
        title: post.title,
        template: "blog",
        subtitle: post.excerpt,
    });

    useEffect(() => {
        const ogImage = document.querySelector('meta[property="og:image"]');
        if (ogImage && ogImageUrl) {
            ogImage.setAttribute("content", ogImageUrl);
        }
    }, [ogImageUrl]);

    return (
        <article>
            <h1>{post.title}</h1>
            <p>{post.excerpt}</p>
        </article>
    );
}

React Helmet (SSR)

jsx
// src/pages/BlogPost.jsx
import { Helmet } from "react-helmet-async";
import { useOgImage } from "../components/OgImage";

export default function BlogPost({ post }) {
    const ogImageUrl = useOgImage({
        title: post.title,
        template: "blog",
        subtitle: post.excerpt,
    });

    return (
        <>
            <Helmet>
                <meta
                    property="og:image"
                    content={ogImageUrl || "/fallback-og.png"}
                />
                <meta property="og:title" content={post.title} />
                <meta property="og:description" content={post.excerpt} />
            </Helmet>
            <article>
                <h1>{post.title}</h1>
            </article>
        </>
    );
}

Next.js (React Framework)

Untuk Next.js, lihat tutorial khusus Next.js App Router dan Next.js Pages Router.

Remix

jsx
// app/routes/blog.$slug.jsx
import { json } from "@remix-run/node";
import { useLoaderData } from "@remix-run/react";
import { generateSignedOgUrl } from "~/lib/og-image-signer.server";

export async function loader({ params }) {
    const post = await getPost(params.slug);

    const ogImageUrl = generateSignedOgUrl({
        template: "blog",
        title: post.title,
        subtitle: post.excerpt,
    });

    return json({ post, ogImageUrl });
}

export function meta({ data }) {
    return [
        { title: data.post.title },
        { property: "og:image", content: data.ogImageUrl },
        { property: "og:title", content: data.post.title },
    ];
}

export default function BlogPost() {
    const { post } = useLoaderData();

    return (
        <article>
            <h1>{post.title}</h1>
        </article>
    );
}

Penanda sisi server (Node.js)

javascript
// lib/og-image-signer.server.js
import crypto from "crypto";

export function generateSignedOgUrl(params, options = {}) {
    const {
        baseUrl = "https://fastog.com/api/v1/og",
        apiKey = process.env.FASTOG_API_KEY,
        hmacSecret = process.env.FASTOG_HMAC_SECRET,
    } = options;

    // RFC-3986 percent-encoding: keep A-Za-z0-9-._~
    const enc = (s) =>
        encodeURIComponent(s).replace(
            /[!'()*]/g,
            (c) => "%" + c.charCodeAt(0).toString(16).toUpperCase(),
        );

    // Every query param except the signature, INCLUDING key
    const all = { ...params, key: apiKey };

    // Canonical query: sorted enc(key)=enc(value) pairs joined with &
    const pairs = [];
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            pairs.push(`${enc(k)}=${enc(vv)}`);
        }
    }
    pairs.sort();
    const canonical = pairs.join("&");

    // Sign the exact bytes the server will verify
    const signature = crypto
        .createHmac("sha256", hmacSecret)
        .update(`GET/api/v1/og\n${canonical}`)
        .digest("hex");

    // Build the URL from the same pairs so bytes match the canonical form
    const url = new URL(baseUrl);
    for (const [k, v] of Object.entries(all)) {
        for (const vv of Array.isArray(v) ? v : [v]) {
            url.searchParams.append(Array.isArray(v) ? `${k}[]` : k, vv);
        }
    }
    url.searchParams.set("s", signature);

    return url.toString();
}

Variabel Lingkungan

bash
# .env (Vite)
VITE_FASTOG_API_KEY=sk_your_full_api_key_here
VITE_FASTOG_HMAC_SECRET=your_64_char_hex_secret_here

# .env (Create React App)
REACT_APP_FASTOG_API_KEY=sk_your_full_api_key_here
REACT_APP_FASTOG_HMAC_SECRET=your_64_char_hex_secret_here

# Server .env
FASTOG_API_KEY=sk_your_full_api_key_here
FASTOG_HMAC_SECRET=your_64_char_hex_secret_here

Kesalahan Umum

Mengekspos Rahasia HMAC pada Kode Klien

❌ Salah:

javascript
// In browser code
const ogUrl = generateSignedOgUrl(params, {
    hmacSecret: import.meta.env.VITE_FASTOG_HMAC_SECRET,
});

✅ Benar:

javascript
// Call your backend API
const res = await fetch(`/api/og?title=${post.title}`);
const { ogImageUrl } = await res.json();

Tidak Memperbarui Tag Meta

Perayap sosial membutuhkan tag meta pada HTML awal. Gunakan SSR (Next.js, Remix) atau proksi backend untuk dukungan gambar OG yang tepat.

Referensi API Lengkap

Coba gratis — tanpa perlu mendaftar

Pratinjau dan uji gambar OG dinamis dalam hitungan detik.

Buka Penguji Gambar OG Gratis
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