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import { CLSMetric, MetricRatingThresholds, ReportOpts } from './types.js';
/** Thresholds for CLS. See https://web.dev/articles/cls#what_is_a_good_cls_score */
export declare const CLSThresholds: MetricRatingThresholds;
/**
* Calculates the [CLS](https://web.dev/articles/cls) value for the current page and
* calls the `callback` function once the value is ready to be reported, along
* with all `layout-shift` performance entries that were used in the metric
* value calculation. The reported value is a `double` (corresponding to a
* [layout shift score](https://web.dev/articles/cls#layout_shift_score)).
*
* If the `reportAllChanges` configuration option is set to `true`, the
* `callback` function will be called as soon as the value is initially
* determined as well as any time the value changes throughout the page
* lifespan.
*
* _**Important:** CLS should be continually monitored for changes throughout
* the entire lifespan of a page—including if the user returns to the page after
* it's been hidden/backgrounded. However, since browsers often [will not fire
* additional callbacks once the user has backgrounded a
* page](https://developer.chrome.com/blog/page-lifecycle-api/#advice-hidden),
* `callback` is always called when the page's visibility state changes to
* hidden. As a result, the `callback` function might be called multiple times
* during the same page load._
*/
export declare const onCLS: (onReport: (metric: CLSMetric) => void, opts?: ReportOpts) => void;
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