softkave-js-utils/build/function/singleton.js

JavaScript & Typescript utility functions, types, and classes

import { isUndefined, noop } from 'lodash-es';
import { cast } from '../other/index.js';
export function singletonFn(initFn, disposeFn = noop) {
    let data = undefined;
    let refs = 0;
    const mainFn = () => {
        refs++;
        if (isUndefined(data)) {
            data = initFn();
        }
        return data;
    };
    const invalidateFn = async () => {
        if (!isUndefined(data)) {
            await disposeFn(data);
        }
        data = undefined;
    };
    const releaseFn = async () => {
        refs--;
        if (refs === 0 && !isUndefined(data)) {
            await disposeFn(data);
            data = undefined;
        }
    };
    cast(mainFn).invalidate = invalidateFn;
    cast(mainFn).release = releaseFn;
    return cast(mainFn);
}
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