getCurrentPosition() 獲取一次用戶位置，適合如“查找最近商店”等單次定位需求；watchPosition() 持續(xù)監(jiān)控位置變化并實時更新，適用于如健身追蹤或?qū)Ш降刃枰掷m(xù)跟蹤的應用。前者獲取位置后自動結束，后者需手動調(diào)用 clearWatch() 停止以避免資源浪費。兩者均可通過設置 enableHighAccuracy、timeout 等參數(shù)優(yōu)化性能，但 watchPosition() 因持續(xù)運行對電池影響更大。

If you're working with geolocation in JavaScript, you might wonder: what's the real difference between watchPosition() and getCurrentPosition()? The short answer is this — getCurrentPosition() gets the user’s location once, while watchPosition() keeps checking and updates whenever the location changes. That’s a key distinction, especially if your app needs live location tracking.

Let’s break it down into more practical terms.

One-Time vs. Continuous Tracking

This is the most obvious difference.

• getCurrentPosition() takes a snapshot of the current location and stops after that. It’s perfect for things like "Find nearest store" features where you only need the location once.

• watchPosition(), on the other hand, works like a watcher. Once you call it, it keeps running in the background, giving you updated location data every time the device detects a change. This is useful for apps like fitness trackers or navigation tools.

Think of it like taking a photo versus recording a video. One gives you a still image, the other keeps updating as movement happens.

How They Handle Updates Differently

Even though both methods use success and error callbacks, they behave differently when handling updates:

• With getCurrentPosition(), the success callback runs once — when the position is retrieved.
• With watchPosition(), the same success callback can run multiple times, each time with a new GeolocationPosition object.

Here’s a basic example of how watchPosition() looks in code:

const watchId = navigator.geolocation.watchPosition(position => {
  console.log("Updated latitude:", position.coords.latitude);
});

You can also stop it later using clearWatch(watchId) — which brings us to another point…

Control Over Execution Matters

Knowing when and how to stop these functions is important for performance and battery life.

• getCurrentPosition() ends automatically after one result.
• watchPosition() will keep going until you manually stop it or the page closes.

So if you're building something like a map app that tracks movement, make sure to clean up by calling navigator.geolocation.clearWatch(watchId) when you no longer need updates. Otherwise, the browser will keep polling for location, which can drain the device’s battery faster.

Accuracy and Performance Considerations

Both methods accept an optional options object where you can set things like enableHighAccuracy, timeout, and maximumAge. But since watchPosition() runs continuously, those settings have a bigger impact over time.

For example:

• If enableHighAccuracy is set to true, the device might switch to GPS mode, which is more accurate but also uses more power.
• A shorter timeout may cause failures if the device struggles to get a fix quickly enough — especially relevant during repeated calls from watchPosition().

So, when choosing between the two methods, consider not just functionality but also how it affects performance and resource usage.

That’s basically it. Use getCurrentPosition() when you want a single location update, and go with watchPosition() when you need ongoing tracking. Keep in mind how long each runs, how often they pull data, and how that affects your app’s behavior and device resources.

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