Changing CSS pseudo-element styles via JavaScript [duplicate]

Answer 1

I changed the background of the ::selection pseudo-element by using CSS custom properties doing the following:

/*CSS Part*/
:root {
    --selection-background: #000000;
}
#editor::selection {
    background: var(--selection-background);
}

//JavaScript Part
document.documentElement.style.setProperty("--selection-background", "#A4CDFF");