Focused Line for readers

focused-line.user.js

(() => {
    'use strict';

    const height = 20;
    const body = document.querySelector('body');
    const focusedLine = document.createElement('div');
    focusedLine.setAttribute('id', 'focused-line');
    body.appendChild(focusedLine);

    focusedLine.style.cssText = `position: absolute; width: 100%; background-color: rgba(230, 228, 63, 0.5); height: ${height}px; z-index: -1; display: none;`;

    document.addEventListener('click', changePosition);

    function changePosition(e) {
        let y = e.clientY;
        y -= parseInt(height) / 2;

        focusedLine.style.display = '';
        focusedLine.style.top = `${y}px`;
    }
})();