Function throttle

src/utils/throttle.ts:1–30

(callback: T)

export function throttle<T extends(...args: any[]) => any>(callback: T): T & {cancel: () => void} {
    let pending = false;
    let frameId: number | null = null;
    let lastArgs: any[];

    const throttled: T = ((...args: any[]) => {
        lastArgs = args;
        if (frameId) {
            pending = true;
        } else {
            callback(...lastArgs);
            frameId = requestAnimationFrame(() => {
                frameId = null;
                if (pending) {
                    callback(...lastArgs);
                    pending = false;
                }
            });
        }
    }) as any;

    const cancel = () => {
        // TODO: resolve cast once types are updated
        cancelAnimationFrame(frameId!);
        pending = false;
        frameId = null;
    };

    return Object.assign(throttled, {cancel});
}

type Task = () => void;