audioDuration.js

const cache = new WeakMap()

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

    const audio = document.createElement('audio')
    audio.addEventListener('loadedmetadata', e => {
        const duration = audio.duration
        cache.set(src, duration)
        resolve(duration)
    })
    audio.addEventListener('error', reject)

    audio.src = src
})