MediaWiki:Common.js

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/* Any JavaScript here will be loaded for all users on every page load. */

if (mw.config.get('wgCanonicalSpecialPageName') === 'Userlogin') {
    const style = document.createElement('style');
    style.textContent = `
        body { background-color: #f0f8ff !important; }
        #mw-content-text { border: 3px solid red !important; }
    `;
    document.head.appendChild(style);
}