Fastest install script for npm 7.0+, speed up npm ci

install.js

// Fastest install script for npm 7.0+
// usage: node install

const fs = require('fs');

const readLockFile = path => {
    if (fs.existsSync(path)) {
        const text = fs.readFileSync(path, { encoding:'utf8', flag:'r' });
        const lockFile = JSON.parse(text);
        delete lockFile.dependencies;
        delete lockFile.lockfileVersion;
        Object.getOwnPropertyNames(lockFile.packages).forEach(p => {
            if (p === '' || lockFile.packages[p].optional) {
                delete lockFile.packages[p];
            }
        });
        return lockFile;
    }
}

const expected = readLockFile('./package-lock.json');

// call npm ci only when package-lock changed
if (expected) {
    const actual = readLockFile('./node_modules/.package-lock.json');
    if (!actual || JSON.stringify(actual) !== JSON.stringify(expected)) {
        const { execSync } = require('child_process');
        execSync('npm ci', { stdio: 'inherit' });
    }
}