1 | /*
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2 | * Copyright 2020 Google LLC
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3 | *
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4 | * Licensed under the Apache License, Version 2.0 (the "License");
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5 | * you may not use this file except in compliance with the License.
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6 | * You may obtain a copy of the License at
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7 | *
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8 | * https://www.apache.org/licenses/LICENSE-2.0
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9 | *
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10 | * Unless required by applicable law or agreed to in writing, software
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11 | * distributed under the License is distributed on an "AS IS" BASIS,
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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13 | * See the License for the specific language governing permissions and
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14 | * limitations under the License.
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15 | */
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16 |
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17 | export interface PerformanceEntryHandler {
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18 | (entry: PerformanceEntry): void;
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19 | }
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20 |
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21 | /**
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22 | * Takes a performance entry type and a callback function, and creates a
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23 | * `PerformanceObserver` instance that will observe the specified entry type
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24 | * with buffering enabled and call the callback _for each entry_.
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25 | *
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26 | * This function also feature-detects entry support and wraps the logic in a
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27 | * try/catch to avoid errors in unsupporting browsers.
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28 | */
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29 | export const observe = (
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30 | type: string,
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31 | callback: PerformanceEntryHandler,
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32 | ): PerformanceObserver | undefined => {
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33 | try {
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34 | if (PerformanceObserver.supportedEntryTypes.includes(type)) {
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35 | const po: PerformanceObserver =
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36 | new PerformanceObserver((l) => l.getEntries().map(callback));
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37 |
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38 | po.observe({type, buffered: true});
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39 | return po;
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40 | }
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41 | } catch (e) {
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42 | // Do nothing.
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43 | }
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44 | return;
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45 | };
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