For an accurate JavaScript timer, measure elapsed time with performance.now() and calculate the timer’s state from that measurement. Treat setTimeout() and setInterval() as requests to run code later—not guarantees that a callback will run at an exact time or on an exact cadence.
Why JavaScript timers drift
A timer API schedules callbacks; it does not measure time for you. A callback can run later than requested, so a countdown that subtracts one second each time its callback fires accumulates lateness. Instead, record a start time or deadline, then derive the current remaining time whenever the callback runs.
For elapsed time within a running context, performance.now() provides a high-resolution timestamp based on a monotonic clock. Unlike Date.now(), it is not affected by system clock adjustments. Its precision may be reduced for security and privacy reasons, and its value is relative to the page’s time origin rather than a wall-clock date. MDN documents the API and its time origin.
Build a duration-based countdown
Capture the starting timestamp once. On each update, subtract elapsed time from the duration and clamp the result at zero:
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
const durationMs = 10_000;
const startedAt = performance.now();
function update() {
const elapsed = performance.now() - startedAt;
const remaining = Math.max(0, durationMs - elapsed);
renderCountdown(remaining);
if (remaining > 0) {
setTimeout(update, 100);
}
}
update();The 100 ms timeout controls how often the display is refreshed; it does not define the countdown’s accuracy. If the page is busy or suspended and an update arrives late, the next calculation reflects the time that actually elapsed instead of carrying the delay forward.
Choose the scheduling API for the job
| Need | Approach | Important limitation |
|---|---|---|
| Measure elapsed time | performance.now() |
Relative to a time origin; precision may be reduced. |
| Run one callback after a delay | setTimeout() |
The callback can be late; browser timeout behavior has minimum-delay and integer-range limits. |
| Repeat a lightweight callback | setInterval() |
Actual callback spacing can exceed the requested delay. |
| Animate visual state | requestAnimationFrame() |
Schedules a one-shot callback before repaint and is generally paused in background tabs or hidden iframes. |
| Run timers in Node.js | Node.js timer APIs | Similar API surface, but a different implementation around the Node.js event loop. |
setTimeout() for periodic display updates
setTimeout() requests a one-time asynchronous callback. It does not promise to run exactly when its delay expires. In browsers, sufficiently nested timeouts are subject to a 4 ms minimum delay, stricter delays may apply in some circumstances, and the delay is bounded by a signed 32-bit millisecond value (2,147,483,647 ms). See MDN’s setTimeout() reference.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
setInterval() for recurring callbacks
setInterval() requests recurring callbacks, but the actual time between callbacks may be longer than the requested interval. If an operation may take longer than the interval, MDN recommends recursive setTimeout() so the next operation is scheduled after the current one completes; this avoids initiating overlapping work. See MDN’s setInterval() reference.
requestAnimationFrame() for animation
For visual animation, use requestAnimationFrame() and calculate progress from its callback timestamp or elapsed time. Do not advance an animation by a fixed amount per frame: displays can refresh at different rates, and animation callbacks are generally paused in background tabs or hidden iframes. The API is one-shot, so request another frame when needed. MDN describes it as a way to request animation work from the browser.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsRank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Node.js timers
Node.js provides timer functions with names and usage similar to browser APIs, but its timers are implemented around the Node.js event loop. Browser-specific behavior should not be assumed to apply identically in Node.js. See the Node.js timers documentation.
Use a deadline when the timer targets a known end time
If a timer should end after a duration, the start-time pattern above works. If it should count down to a target within the running page, record a deadline using the same monotonic clock, then compute deadline - performance.now() on each update. In either case, schedule updates at a suitable cadence, but derive the displayed value from the clock rather than decrementing it because a callback ran.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
What “accurate” can and cannot mean
These techniques keep elapsed-time calculations from accumulating callback delays. They do not make the callback itself punctual: the browser or Node.js runtime may run it later than requested. Choose the mechanism according to whether you need accurate elapsed-time measurement, smooth visual updates, a particular callback cadence, or behavior in a specific runtime; none guarantees execution at an exact wall-clock instant.
Quick Recap
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Free tools Windows power users keep installed
One-click scans. No signup required.
