build-404-page.mjs
#!/usr/bin/env node
// Imports
import {readFileSync, writeFileSync} from 'fs';
import {join, resolve} from 'path';
// Constants
const SOURCE_404_BODY_PATH = resolve(process.argv[2]);
const BUILD_OUTPUT_DIR = resolve(process.argv[3]);
const DEST_404_PAGE_PATH = resolve(process.argv[4]);
// Run
_main();
// Functions - Definitions
function _main() {
const srcIndexPath = join(BUILD_OUTPUT_DIR, 'index.html');
const srcIndexContent = readFileSync(srcIndexPath, 'utf8');
const src404BodyContent = readFileSync(SOURCE_404_BODY_PATH, 'utf8').trim();
const dst404PageContent = srcIndexContent.replace(
/(<body>)[\s\S]+(<\/body>)/,
`$1\n ${src404BodyContent}\n$2`
);
if (dst404PageContent === srcIndexContent) {
throw new Error(
"Failed to generate '404.html'. " +
"The content of 'index.html' does not match the expected pattern."
);
}
writeFileSync(DEST_404_PAGE_PATH, dst404PageContent);
}