<button>Hello</button>
<script>
    const btn = document.querySelector('button');
    btn.addEventListener('click', () => alert('World!'));
</script>
Hello
<a href="javascript:alert('World!')">Hello</a>
Hello
const style = document.createElement('style');
style.innerText = 'a,a:hover,a:focus,a:visited{color: yellow;}';
document.head.append(style)
<a href="javascript:(() => {
    const style = document.createElement('style');
    style.innerText = 'a,a:hover,a:focus,a:visited{color: yellow;}';
    document.head.append(style);
})()">Hello</a>
Search here
<a href="javascript:(() => {
    const currentUrl = document.location.href;
    const googleSearchUrl = `https://www.google.fr/search?q=url%3A${currentUrl}%2F`;
    document.location.replace(googleSearchUrl);
})()">Search here</a>
Show undefined/null class
<a href="javascript:(() => {
    const style = document.createElement('style');
    style.innerText = '.undefined,.null{border: 1px solid red;}';
    document.head.append(style);
})()">Show undefined/null class</a>
Show elements with e2e selector
<a href="javascript:(() => {
    const style = document.createElement('style');
    style.innerText = `
    [data-e2e]{border: 3px dashed green;}
    [data-auto]{border: 3px dashed orange;}
    [e2e-id]{border: 3px dashed blue;}
    `;
    document.head.append(style);
})()">Show elements with e2e selector</a>
Send me as SMS
<a href="javascript:(() => {
    const msg = window.getSelection() || 'nothing selected';
    fetch(`https://smsapi.free-mobile.fr/sendmsg?user=${SECRETS.user}&pass=${SECRETS.pass}&msg=${encodeURI(msg)}`);
})()">Send me as SMS</a>