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getScroll.ts
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getScroll.ts
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export function isWindow(obj: any): obj is Window {
return obj !== null && obj !== undefined && obj === obj.window;
}
export default function getScroll(
target: HTMLElement | Window | Document | null,
top: boolean,
): number {
if (typeof window === 'undefined') {
return 0;
}
const method = top ? 'scrollTop' : 'scrollLeft';
let result = 0;
if (isWindow(target)) {
result = target[top ? 'pageYOffset' : 'pageXOffset'];
} else if (target instanceof Document) {
result = target.documentElement[method];
} else if (target instanceof HTMLElement) {
result = target[method];
} else if (target) {
// According to the type inference, the `target` is `never` type.
// Since we configured the loose mode type checking, and supports mocking the target with such shape below::
// `{ documentElement: { scrollLeft: 200, scrollTop: 400 } }`,
// the program may falls into this branch.
// Check the corresponding tests for details. Don't sure what is the real scenario this happens.
result = target[method];
}
if (target && !isWindow(target) && typeof result !== 'number') {
result = (target.ownerDocument ?? target).documentElement?.[method];
}
return result;
}