Display time in page title using JS

A fun 2008 trick: a snippet (credited to Mike Cullen, featured on Dynamic Drive) that updated document.title every second so the tab showed a live clock — “TIME: 3:42:17 P.M.” visible even when the page was in a background tab.

Why the original code wouldn’t run today

The 1999-era script is a museum piece of dead patterns:

• document.all — IE-only detection, meaningless since evergreen browsers won
• setTimeout("scroll()", 1000) — string-form timer evaluation (the function name also shadowed window.scroll)
• A 12-branch if/else chain just to convert 24h → 12h time
• HTML comment hiding (<!-- Hide) for Netscape 2-era parsers
• Globals for hr, min, sec mutated across three functions

The same effect in a dozen lines

Writing to the document title from a timer still works identically — that part of the DOM hasn’t changed. The modern version:

const baseTitle = document.title;

function tick() {
  const now = new Date();
  document.title = baseTitle + ' — ' +
    now.toLocaleTimeString(undefined, { hour: 'numeric', minute: '2-digit', second: '2-digit' });
}

tick();
setInterval(tick, 1000);

toLocaleTimeString handles the 12/24-hour question, the AM/PM suffix and zero-padding automatically using the visitor’s locale — all those if branches for free. The function-return form of setInterval avoids string evaluation entirely.

If you want full control over formatting (padded 24-hour, custom separators), reach for Intl.DateTimeFormat — build one formatter up front and call .format(now) each tick rather than re-parsing options every second.

Two practical notes

First, a per-second title update is wasted work when the tab is hidden: modern browsers throttle background-tab timers anyway, but it’s cleaner to check document.visibilityState and skip the update while hidden. Second, remember the title is also what bookmarks and screen readers announce — a title that permanently reads “TIME: 4:03:56 P.M.” is hostile to both, so restore baseTitle on pagehide or stop the timer after some idle period.

As a 2008 novelty it was neat; as a lesson it’s better than the original: the DOM API kept working for 27 years, while everything around it rotted.