The changedTouches read-only property is a TouchList whose touch points (Touch objects) varies depending on the event type, as follows:
touchstart event, it is a list of the touch points that became active with the current event.touchmove event, it is a list of the touch points that have changed since the last event.touchend and touchcancel events, it is a list of the touch points that have been removed from the surface (that is, the set of touch points corresponding to fingers no longer touching the surface).A TouchList whose Touch objects include all the touch points that contributed to this touch event.
This example illustrates the TouchEvent object's TouchEvent.changedTouches property. The TouchEvent.changedTouches property is a TouchList object that contains one Touch object for each touch point which contributed to the event.
In following code snippet, the touchmove event handler iterates through the changedTouches list and prints the identifier of each touch point that changed since the last event.
someElement.addEventListener("touchmove", (e) => {
// Iterate through the list of touch points that changed
// since the last event and print each touch point's identifier.
for (let i = 0; i < e.changedTouches.length; i++) {
console.log(
`changedTouches[${i}].identifier = ${e.changedTouches[i].identifier}`,
);
}
});