web-vitals
Version:
Easily measure performance metrics in JavaScript
33 lines (32 loc) • 1.21 kB
JavaScript
/*
* Copyright 2024 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const instanceMap = new WeakMap();
/**
* A function that accepts and identity object and a class object and returns
* either a new instance of that class or an existing instance, if the
* identity object was previously used.
*/
export function initUnique(identityObj, ClassObj) {
let classInstances = instanceMap.get(ClassObj);
if (!classInstances) {
classInstances = new WeakMap();
instanceMap.set(ClassObj, classInstances);
}
if (!classInstances.get(identityObj)) {
classInstances.set(identityObj, new ClassObj());
}
return classInstances.get(identityObj);
}