@chasemoskal/magical/x/element/setup-use-object-for-element.js

web toolkit for lit apps

export const setupUseObjectForElement = ({ addSetup, rerender, getRenderCount, incrementStateCount, }) => {
    const stateMap = new Map();
    return {
        setup: initializer => {
            if (getRenderCount() === 0)
                addSetup(initializer);
        },
        state: initial => {
            const count = incrementStateCount();
            const alreadySet = stateMap.has(count);
            let currentValue;
            let previousValue;
            if (alreadySet)
                [currentValue, previousValue] = stateMap.get(count) ?? [];
            else
                stateMap.set(count, [
                    currentValue =
                        (typeof initial === "function")
                            ? initial()
                            : initial,
                    undefined,
                ]);
            const setter = valueOrFunction => {
                const previousValue = getter();
                const newValue = (typeof valueOrFunction === "function")
                    ? valueOrFunction(previousValue)
                    : valueOrFunction;
                stateMap.set(count, [newValue, previousValue]);
                rerender();
            };
            const getter = () => (stateMap.get(count) ?? [])[0];
            return [
                currentValue,
                setter,
                getter,
                previousValue,
            ];
        },
    };
};
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