Update README

README.md

@@ -490,7 +490,75 @@ For guidance on how to collect and use real-user data to debug performance issue
 
 ### Types
 
-#### Metrics
+#### `Metric`
+
+All metrics types inherit from the following base interface:
+
+```ts
+interface Metric {
+  /**
+   * The name of the metric (in acronym form).
+   */
+  name: 'CLS' | 'FCP' | 'FID' | 'INP' | 'LCP' | 'TTFB';
+
+  /**
+   * The current value of the metric.
+   */
+  value: number;
+
+  /**
+   * The rating as to whether the metric value is within the "good",
+   * "needs improvement", or "poor" thresholds of the metric.
+   */
+  rating: 'good' | 'needs-improvement' | 'poor';
+
+  /**
+   * The delta between the current value and the last-reported value.
+   * On the first report, `delta` and `value` will always be the same.
+   */
+  delta: number;
+
+  /**
+   * A unique ID representing this particular metric instance. This ID can
+   * be used by an analytics tool to dedupe multiple values sent for the same
+   * metric instance, or to group multiple deltas together and calculate a
+   * total. It can also be used to differentiate multiple different metric
+   * instances sent from the same page, which can happen if the page is
+   * restored from the back/forward cache (in that case new metrics object
+   * get created).
+   */
+  id: string;
+
+  /**
+   * Any performance entries relevant to the metric value calculation.
+   * The array may also be empty if the metric value was not based on any
+   * entries (e.g. a CLS value of 0 given no layout shifts).
+   */
+  entries: PerformanceEntry[];
+
+  /**
+   * The type of navigation.
+   *
+   * This will be the value returned by the Navigation Timing API (or
+   * `undefined` if the browser doesn't support that API), with the following
+   * exceptions:
+   * - 'back-forward-cache': for pages that are restored from the bfcache.
+   * - 'back_forward' is renamed to 'back-forward' for consistency.
+   * - 'prerender': for pages that were prerendered.
+   * - 'restore': for pages that were discarded by the browser and then
+   * restored by the user.
+   */
+  navigationType:
+    | 'navigate'
+    | 'reload'
+    | 'back-forward'
+    | 'back-forward-cache'
+    | 'prerender'
+    | 'restore';
+}
+```
+
+Metric-specific subclasses:
 
 ##### [`CLSMetric`](/src/types/cls.ts#:~:text=interface%20CLSMetric)
 
@@ -546,62 +614,6 @@ interface TTFBMetric extends Metric {
 }
 ```
 
-##### `Metric`
-
-All metrics share the following properties:
-
-```ts
-interface Metric {
-  /**
-   * The current value of the metric.
-   */
-  value: number;
-
-  /**
-   * The rating as to whether the metric value is within the "good",
-   * "needs improvement", or "poor" thresholds of the metric.
-   */
-  rating: 'good' | 'needs-improvement' | 'poor';
-
-  /**
-   * The delta between the current value and the last-reported value.
-   * On the first report, `delta` and `value` will always be the same.
-   */
-  delta: number;
-
-  /**
-   * A unique ID representing this particular metric instance. This ID can
-   * be used by an analytics tool to dedupe multiple values sent for the same
-   * metric instance, or to group multiple deltas together and calculate a
-   * total. It can also be used to differentiate multiple different metric
-   * instances sent from the same page, which can happen if the page is
-   * restored from the back/forward cache (in that case new metrics object
-   * get created).
-   */
-  id: string;
-
-  /**
-   * The type of navigation.
-   *
-   * This will be the value returned by the Navigation Timing API (or
-   * `undefined` if the browser doesn't support that API), with the following
-   * exceptions:
-   * - 'back-forward-cache': for pages that are restored from the bfcache.
-   * - 'back_forward' is renamed to 'back-forward' for consistency.
-   * - 'prerender': for pages that were prerendered.
-   * - 'restore': for pages that were discarded by the browser and then
-   * restored by the user.
-   */
-  navigationType:
-    | 'navigate'
-    | 'reload'
-    | 'back-forward'
-    | 'back-forward-cache'
-    | 'prerender'
-    | 'restore';
-}
-```
-
 #### `MetricRatingThresholds`
 
 The thresholds of metric's "good", "needs improvement", and "poor" ratings.