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perf(drag-drop): use narrower check for touch events #16082

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Merged
merged 1 commit into from
Jun 19, 2019
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perf(drag-drop): use narrower check for touch events #16082

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5 changes: 4 additions & 1 deletion src/cdk/drag-drop/drag-ref.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1103,7 +1103,10 @@ function removeElement(element: HTMLElement | null) {

/** Determines whether an event is a touch event. */
function isTouchEvent(event: MouseEvent | TouchEvent): event is TouchEvent {
return event.type.startsWith('touch');
// This function is called for every pixel that the user has dragged so we need it to be
// as fast as possible. Since we only bind mouse events and touch events, we can assume
// that if the event's name starts with `t`, it's a touch event.
return event.type[0] === 't';
}

/** Gets the element into which the drag preview should be inserted. */
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