getAudioDuration.js

const cache = new Map()

export default src =>
    new Promise((resolve, reject) => {
        if (cache.has(src)) resolve(cache.get(src))

        const audio = document.createElement('audio')

        audio.addEventListener('loadedmetadata', () => {
            const duration = audio.duration

            // Along comes Chrome
            // Unfortunately, there is currently a Chromium bug that causes the duration not to be available under certain circumstances. In these conditions, you will see the video or audio duration as being Infinity (a vestige of the infinite stream concept, presumably).
            if (duration === Infinity) {
                const ontimeupdate = () => {
                    const duration = audio.duration

                    cache.set(src, duration)
                    resolve(duration)

                    audio.currentTime = 0
                    audio.removeEventListener('timeupdate', ontimeupdate)
                }

                audio.addEventListener('timeupdate', ontimeupdate)

                audio.currentTime = 1e101

                return
            }

            cache.set(src, duration)
            resolve(duration)
        })
        audio.addEventListener('error', reject)

        audio.src = src
    })

// http://victorblog.com/2018/02/14/get-video-and-audio-blob-duration-in-html5/