Get Media File Duration In Seconds (With Low-Budget Caching)

get-media-duration.ts

/**
 * Get media file duration in seconds.
 */
export function getMediaDuration(file: File): Promise<number> {
    if (!window.getMediaDurationCache) {
        window.getMediaDurationCache = new WeakMap();
    }

    const cached = window.getMediaDurationCache.get(file);

    if (cached !== undefined) {
        return Promise.resolve(cached);
    }

    return new Promise(resolve => {
        const isVideo = file.type.startsWith('video/');

        const media = document.createElement(isVideo ? 'video' : 'audio');

        const objectUrl = URL.createObjectURL(file);

        media.preload = 'metadata';

        media.src = objectUrl;

        media.onloadedmetadata = () => {
            const duration = media.duration;

            URL.revokeObjectURL(objectUrl);

            media.remove();

            window.getMediaDurationCache.set(file, duration);

            resolve(duration);
        };

        media.onerror = e => {
            URL.revokeObjectURL(objectUrl);

            media.remove();

            console.error(e);

            resolve(0);
        };
    });
}