Next.js post export script to change url file paths to relative ones

relativateCssUrls.js

const fs = require('fs');
const proc = require('process');
const path = require('path');

function modifyUrl(content, depth) {
    let replacementArray = [];
    for (let i = 0; i < depth; i++) {
        replacementArray.push('..');
    }
    let replacement = replacementArray.join('/');
    if (replacementArray.length > 0) {
        replacement = `${replacement}/`;
    }
    return content.replace(/url\("\//gm, `url("${replacement}`)
        .replace(/url\('\//gm, `url('${replacement}`)
        .replace(/url\(\//gm, `url(${replacement}`)
}

function convertToRelativeFilePaths(directory, depth = 0, extensionRegex = /^\.css$/) {
    fs.readdir(directory, (error, files) => {
        if (error) {
            console.error(`Unable to list directory ${directory}`, error);
            proc.exit(1)
        }

        files.forEach((file, index) => {
            let absolutePath = path.join(directory, file);

            fs.stat(absolutePath, (error, stat) => {
                if (error) {
                    console.error(`Unable to stat path ${absolutePath}`, error);
                    return
                }
                if (stat.isFile()) {
                    let extension = path.extname(absolutePath);
                    if (!extensionRegex.test(extension)) {
                        return
                    }
                    console.debug(`Processing file ${absolutePath}`);
                    fs.readFile(absolutePath, 'utf8', (error, data) => {
                        if (error) {
                            console.error(`Unable to read file ${absolutePath}`, error);
                            return
                        }
                        let result = modifyUrl(data, depth);
                        fs.writeFile(absolutePath, result, error => {
                            if (error) {
                                console.error(error)
                            }
                        });
                    });
                } else if (stat.isDirectory()) {
                    convertToRelativeFilePaths(absolutePath, depth + 1)
                } else {
                    console.warn(`Unknown file stat for ${absolutePath}`)
                }
            });
        });
    });
}

// call like `node relativateCssUrls.js out`
convertToRelativeFilePaths(proc.argv[2]);

This is needed because I am tired of spending hours and days on JS/TS project setups.