@vtbag/utensil-drawer/lib/view-transition-surrogate.js

Pull out just what you need to craft seamless transitions. The Utensil Drawer holds reusable functions to help you build websites with view transitions. It is a bit sparse right now, but like the one in your kitchen, it is bound to fill up over time.

export function createViewTransitionSurrogate(update) {
    let res;
    let rej;
    let readyReject;
    const updateCallbackDone = new Promise((resolve, reject) => {
        res = resolve;
        rej = reject;
    });
    let updateFailure = undefined;
    requestAnimationFrame(async () => {
        try {
            await update();
            res();
        }
        catch (e) {
            updateFailure = e;
            rej(e);
        }
    });
    const ready = new Promise((res, rej) => {
        readyReject = rej;
        updateCallbackDone.then(() => res(), //rej('Browser does not support View Transition API'),
        (_) => res() //rej(err)
        );
    });
    const done = (res, rej) => updateFailure ? rej(updateFailure) : res();
    const finished = new Promise((res, rej) => updateCallbackDone.finally(() => ready.then(() => done(res, rej), (e) => done(res, rej))));
    return {
        updateCallbackDone,
        ready,
        finished,
        skipTransition: () => { },
        types: new Set(),
    };
}