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@@ -340,12 +340,16 @@ The high resolution millisecond timestamp at which the V8 platform was |
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initialized. |
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## Class: PerformanceObserver(callback) |
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## Class: PerformanceObserver |
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### new PerformanceObserver(callback) |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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* `callback` {Function} A `PerformanceObserverCallback` callback function. |
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* `callback` {Function} |
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* `list` {PerformanceObserverEntryList} |
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* `observer` {PerformanceObserver} |
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`PerformanceObserver` objects provide notifications when new |
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`PerformanceEntry` instances have been added to the Performance Timeline. |
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@@ -364,69 +368,16 @@ obs.observe({ entryTypes: ['mark'], buffered: true }); |
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performance.mark('test'); |
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``` |
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Because `PerformanceObserver` instances introduce their own additional |
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performance overhead, instances should not be left subscribed to notifications |
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indefinitely. Users should disconnect observers as soon as they are no |
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longer needed. |
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### Callback: PerformanceObserverCallback(list, observer) |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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* `list` {PerformanceObserverEntryList} |
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* `observer` {PerformanceObserver} |
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The `PerformanceObserverCallback` is invoked when a `PerformanceObserver` is |
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The `callback` is invoked when a `PerformanceObserver` is |
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notified about new `PerformanceEntry` instances. The callback receives a |
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`PerformanceObserverEntryList` instance and a reference to the |
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`PerformanceObserver`. |
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### Class: PerformanceObserverEntryList |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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The `PerformanceObserverEntryList` class is used to provide access to the |
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`PerformanceEntry` instances passed to a `PerformanceObserver`. |
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#### performanceObserverEntryList.getEntries() |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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* Returns: {PerformanceEntry[]} |
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Returns a list of `PerformanceEntry` objects in chronological order |
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with respect to `performanceEntry.startTime`. |
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#### performanceObserverEntryList.getEntriesByName(name[, type]) |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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* `name` {string} |
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* `type` {string} |
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* Returns: {PerformanceEntry[]} |
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Returns a list of `PerformanceEntry` objects in chronological order |
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with respect to `performanceEntry.startTime` whose `performanceEntry.name` is |
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equal to `name`, and optionally, whose `performanceEntry.entryType` is equal to |
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`type`. |
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#### performanceObserverEntryList.getEntriesByType(type) |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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* `type` {string} |
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* Returns: {PerformanceEntry[]} |
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Returns a list of `PerformanceEntry` objects in chronological order |
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with respect to `performanceEntry.startTime` whose `performanceEntry.entryType` |
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is equal to `type`. |
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### performanceObserver.disconnect() |
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<!-- YAML |
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added: v8.5.0 |
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@@ -482,6 +433,51 @@ for (let n = 0; n < 3; n++) |
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performance.mark(`test${n}`); |
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``` |
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## Class: PerformanceObserverEntryList |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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The `PerformanceObserverEntryList` class is used to provide access to the |
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`PerformanceEntry` instances passed to a `PerformanceObserver`. |
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### performanceObserverEntryList.getEntries() |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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* Returns: {PerformanceEntry[]} |
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Returns a list of `PerformanceEntry` objects in chronological order |
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with respect to `performanceEntry.startTime`. |
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### performanceObserverEntryList.getEntriesByName(name[, type]) |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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* `name` {string} |
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* `type` {string} |
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* Returns: {PerformanceEntry[]} |
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Returns a list of `PerformanceEntry` objects in chronological order |
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with respect to `performanceEntry.startTime` whose `performanceEntry.name` is |
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equal to `name`, and optionally, whose `performanceEntry.entryType` is equal to |
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`type`. |
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### performanceObserverEntryList.getEntriesByType(type) |
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<!-- YAML |
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added: v8.5.0 |
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--> |
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* `type` {string} |
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* Returns: {PerformanceEntry[]} |
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Returns a list of `PerformanceEntry` objects in chronological order |
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with respect to `performanceEntry.startTime` whose `performanceEntry.entryType` |
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is equal to `type`. |
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## Examples |
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### Measuring the duration of async operations |
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