3 ms·

Sounds like the pattern attribute and :invalid selector on <input> will do that. https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#attr-pattern h

• thefifthsetpin 9y ago
  What if it's valid? There's a reason we have the phrases "in the red" and "in the black." Another example where reading the input might be nice: input[type="cc-number"][value^="4"]+.cc-system-icon { background-image: url('visa.png'); }input[type="cc-number"][value^="5"]+.cc-system-icon { background-image: url('master-card.png'); }