NextJS
This was tested against next v13.1.1
on 2023 January 14.
At a high level, there are two ways to pull spreadsheet data into NextJS apps:
loading an asset module or performing the file read operations from the NextJS
lifecycle. At the time of writing, NextJS does not offer an out-of-the-box
asset module solution, so this demo focuses on raw operations. NextJS does not
watch the spreadsheets, so next dev
hot reloading will not work!
The general strategy with NextJS apps is to generate HTML snippets or data from the lifecycle functions and reference them in the template.
HTML output can be generated using XLSX.utils.sheet_to_html
and inserted into
the document using the dangerouslySetInnerHTML
attribute:
export default function Index({html, type}) { return (
// ...
<div dangerouslySetInnerHTML={{ __html: html }} />
// ...
); }
fs
cannot be statically imported from the top level in NextJS pages. The
dynamic import must happen within a lifecycle function. For example:
/* it is safe to import the library from the top level */
import { readFile, utils, set_fs } from 'xlsx';
/* it is not safe to import 'fs' from the top level ! */
// import * as fs from 'fs'; // this will fail
import { join } from 'path';
import { cwd } from 'process';
export async function getServerSideProps() {
set_fs(await import("fs")); // dynamically import 'fs' when needed
const wb = readFile(join(cwd(), "public", "sheetjs.xlsx")); // works
// ...
}
Next 13 switched to the SWC minifier. There are known issues with the minifier.
Until those issues are resolved, SWC should be disabled in next.config.js
:
module.exports = {
swcMinify: false
};
NextJS Strategies
NextJS currently provides 3 strategies:
- "Static Site Generation" using
getStaticProps
- "SSG with Dynamic Routes" using
getStaticPaths
- "Server-Side Rendering" using
getServerSideProps
Static Site Generation
When using getStaticProps
, the file will be read once during build time.
import { readFile, set_fs, utils } from 'xlsx';
export async function getStaticProps() {
/* read file */
set_fs(await import("fs"));
const wb = readFile(path_to_file)
/* generate and return the html from the first worksheet */
const html = utils.sheet_to_html(wb.Sheets[wb.SheetNames[0]]);
return { props: { html } };
};
Dynamic Routes
Typically a static site with dynamic routes has an endpoint /sheets/[id]
that
implements both getStaticPaths
and getStaticProps
.
getStaticPaths
should return an array of worksheet indices:
export async function getStaticPaths() {
/* read file */
set_fs(await import("fs"));
const wb = readFile(path);
/* generate an array of objects that will be used for generating pages */
const paths = wb.SheetNames.map((name, idx) => ({ params: { id: idx.toString() } }));
return { paths, fallback: false };
};
For a pure static site, fallback
must be set to false
!
getStaticProps
will generate the actual HTML for each page:
export async function getStaticProps(ctx) {
/* read file */
set_fs(await import("fs"));
const wb = readFile(path);
/* get the corresponding worksheet and generate HTML */
const ws = wb.Sheets[wb.SheetNames[ctx.params.id]]; // id from getStaticPaths
const html = utils.sheet_to_html(ws);
return { props: { html } };
};
Server-Side Rendering
These routes require a NodeJS dynamic server. Static page generation will fail!
getStaticProps
and getStaticPaths
support static site generation (SSG).
getServerSideProps
is suited for NodeJS hosted deployments where the workbook
changes frequently and a static site is undesirable.
When using getServerSideProps
, the file will be read on each request.
import { readFile, set_fs, utils } from 'xlsx';
export async function getServerSideProps() {
/* read file */
set_fs(await import("fs"));
const wb = readFile(path_to_file);
/* generate and return the html from the first worksheet */
const html = utils.sheet_to_html(wb.Sheets[wb.SheetNames[0]]);
return { props: { html } };
};
Demo
0) Disable NextJS telemetry:
npx [email protected]13.1.1 telemetry disable
Confirm it is disabled by running
npx [email protected]13.1.1 telemetry status
1) Set up folder structure. At the end, a pages
folder with a sheets
subfolder must be created. On Linux or MacOS or WSL:
mkdir -p pages/sheets/
2) Download the test file and place in the project root. On Linux or MacOS or WSL:
curl -LO https://docs.sheetjs.com/next/sheetjs.xlsx
3) Install dependencies:
npm i --save https://cdn.sheetjs.com/xlsx-latest/xlsx-latest.tgz [email protected]
4) Download test scripts:
Download and place the following scripts in the pages
subfolder:
Download [id].js
and place in the
pages/sheets
subfolder.
The [id].js
script must have the literal square brackets in the name. If your
browser saved the file to %5Bid%5D.js
. rename the file.
On Linux or MacOS or WSL:
cd pages
curl -LO https://docs.sheetjs.com/next/index.js
curl -LO https://docs.sheetjs.com/next/getServerSideProps.js
curl -LO https://docs.sheetjs.com/next/getStaticPaths.js
curl -LO https://docs.sheetjs.com/next/getStaticProps.js
cd sheets
curl -LOg 'https://docs.sheetjs.com/next/[id].js'
cd ../..
5) Test the deployment:
Open a web browser and access:
- http://localhost:3000 landing page
- http://localhost:3000/getStaticProps shows data from the first sheet
- http://localhost:3000/getServerSideProps shows data from the first sheet
- http://localhost:3000/getStaticPaths shows a list (3 sheets)
The individual worksheets are available at
- http://localhost:3000/sheets/0
- http://localhost:3000/sheets/1
- http://localhost:3000/sheets/2
6) Stop the server and run a production build:
npx [email protected] build
The final output will show a list of the routes and types:
Route (pages) Size First Load JS
┌ ○ / 541 B 77.4 kB
├ ○ /404 181 B 73.7 kB
├ λ /getServerSideProps 594 B 77.4 kB
├ ● /getStaticPaths 2.56 kB 79.4 kB
├ ● /getStaticProps 591 B 77.4 kB
└ ● /sheets/[id] (447 ms) 569 B 77.4 kB
├ /sheets/0
├ /sheets/1
└ /sheets/2
As explained in the summary, the /getStaticPaths
and /getStaticProps
routes
are completely static. 3 /sheets/#
pages were generated, corresponding to 3
worksheets in the file. /getServerSideProps
is server-rendered.
7) Try to build a static site:
npx [email protected] export
A static page cannot be generated at this point because /getServerSideProps
is still server-rendered.
8) Delete pages/getServerSideProps.js
and rebuild:
rm -f pages/getServerSideProps.js
npx [email protected] build
Inspecting the output, there should be no lines with the λ
symbol:
Route (pages) Size First Load JS
┌ ○ / 541 B 77.4 kB
├ ○ /404 181 B 73.7 kB
├ ● /getStaticPaths 2.56 kB 79.4 kB
├ ● /getStaticProps 591 B 77.4 kB
└ ● /sheets/[id] (459 ms) 569 B 77.4 kB
├ /sheets/0
├ /sheets/1
└ /sheets/2
9) Generate the static site:
npx [email protected] export
The static site will be written to the out
subfolder, which can be hosted with
npx http-server out
The command will start a local HTTP server for testing the generated site. Note
that /getServerSideProps
will 404 since the page was removed.