fileblobSrc.js

const cache = new WeakMap()

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

    const reader = new FileReader()
    reader.addEventListener('load', e => {
        const src = e.target.result
        cache.set(fileblob, src)
        resolve(src)
    })
    reader.addEventListener('error', reject)

    reader.readAsDataURL(fileblob)
})