Read a File using a FileReader returning a jQuery promise

gistfile1.js

function readFile(file) {
    var reader = new FileReader();
    var deferred = $.Deferred();

    reader.onload = function(event) {
        deferred.resolve(event.target.result);
    };

    reader.onerror = function() {
        deferred.reject(this);
    };

    if (/^image/.test(file.type)) {
        reader.readAsDataURL(file);
    } else {
        reader.readAsText(file);
    }

    return deferred.promise();
}

this is interesting. does the file parameter get populated straight off an reference, for instance?

Thanks for this!

Man this is useful. Thanks.

And how to use the Promise.all() in filereader()?

+1

Thanks so much! It really works!

Use w Promise.all like any other:

//Assuming files is object of type FileList
var promises = [];
for (var i = 0; i < files.length; i++) {
    var promise = readFile(files[i]);
    promises.push(promise);
}
Promise.all(promises).then(function(arrayOfDataUrlsAndTextStrings) {
    //Do stuff
})

Exactly what I needed, thank you @jollytoad !