ejs-template-server

Ever wanted to automatically generate OpenGraph images based on a set of input parameters? This package makes it possible to spin up a short-lived server that can tranform a given template on request based un URL query parameters using a simple API.

Installation

For most use cases, installing this package as a devDependency should be enough.

Yarn

yarn add -D ejs-template-server

NPM

npm install -D ejs-template-server

Usage

Simple

Add HTML with EJS syntax to the raw config option. When the server is created, EJS will parse the input for required variables, and will subsequently accept requests that contain these variables in its query params.

server.ts

import { createEjsTemplateServer } from 'ejs-template-server'
import { URLSearchParams } from 'url'
import axios from 'axios'

createEjsTemplateServer({
  template: {
    path: '/og-template.html',
  },
})
  .then(() => {
    const params = new URLSearchParams({
      title: 'Hello world!',
    }).toString()

    const result = axios.get(`http://localhost:8080?${params}`)

    // Do what you want with the result, see the advanced section for an example
  })
  .catch((e) => {
    console.log('The server was unable to start.', e)
    exit(1)
  })

Advanced

Add the path to a file that you want to use as a template to the path config option. Like in the simple example, EJS will automatically recognize required parameters and check the query parameters for these.

In this example, however, playwright is used in order to programatically open the page and take a screenshot at a certain size.

server.ts

import fs from 'fs'
import { createEjsTemplateServer } from 'ejs-template-server'
import { fileURLToPath, URLSearchParams } from 'url'
import { launchChromium } from 'playwright-aws-lambda'

const PORT = 8081

createEjsTemplateServer({
  template: {
    path: 'og-template.html',
  },
  staticParams: {
    getFontSize: (title: string) => (title?.length > 32 ? `text-7xl` : `text-9xl`),
  },
  port: PORT,
})
  .then(() => {
    generateImage('http://localhost:' + PORT)
  })
  .catch((e) => {
    console.log('The server was unable to start.', e)
    exit(1)
  })

function generateImage(url: string) {
  const params = new URLSearchParams({
    title: 'Hello world!',
    date: '2021-11-20',
    readTime: '2 minutes',
  }).toString()

  const url = `${baseURL}?${new URLSearchParams(params).toString()}`

  try {
    const browser = await launchChromium({ headless: true })
    const page = await browser.newPage()
    await page.setViewportSize({ width: 1200, height: 630 })
    await page.goto(url, { waitUntil: 'networkidle' })

    const buffer = await page.screenshot({ type: 'png' })
    await browser.close()

    fs.writeFileSync('output.png', buffer)
  } catch (error) {
    console.error(`An error occurred while generating the image.`, error)
    exit(1)
  }
}

og-template.html

<main>
  <p>
    <% if (date) { %>
    <span><%= date %></span>
    <% } %> — <% if (readTime) { %>
    <span><%= readTime %></span>
    <% } %>
  </p>
  <h1 class="<%= getFontSize(title) %>"><%= title %></h1>
</main>

Options

The createEjsTemplateServer function only requires that you provide a template (path or raw), but there are a few other options as well.

Option	Description	Required	Type	Default
template	An object containing either a raw or a path key respectively.	yes	{ raw?: string, path?: string }
port	The port that the server should listen on.	no	8080	8080
staticParams	Non-changing parameters that should be available at all times in the EJS scope.	no	Record<string, string | ((params: unknown) => unknown)>

Contributing

For guidelines and useful information, please see CONTRIBUTING.md

License

MIT