Bluebird .map promise ends prematurely?

Question

I'm running into a little trouble in my promise code where my Promise.map seems to end prematurely. I'm sure it's a problem with my logic but with the code I'm unsure how to debug it.

Currently, it outputs [], B, A, A with a blobList of size 2. How can I have it so that it finishes pushing to imgList and thus outputs A, A, [*some base64 encoding here*], B where in the .then function, imgList should not be empty?

blobToBase64 Function

blobToBase64(blob, cb) {
  var reader = new window.FileReader();
    reader.readAsDataURL(blob); 

    reader.onloadend = function() {
        let base64data = reader.result;
        cb(base64data);
    }
}

Main function

Promise.map(blobList, function(blobObj){
    helper.blobToBase64(blobObj.data, (fn) => {
        imgList.push(fn);
        console.log('A');
    })
}).then(function(){
    console.log(imgList);
    console.log('B');
})

Answer 1

Here you go:

var promises = blobList.map((blobObj) => {
    return new Promise((resolve, reject) => {
        helper.blobToBase64(blobObj.data, (fn) => {
            imgList.push(fn);
            console.log('A');
            return resolve();
        })
    })
})

Promise
    .all(promises)
    .then(() => {
        console.log(imgList);
        console.log('B');
    })