Read Blobs (and Files) easily. Intended for use with browsers and environments that implement the File API.
Reading binary data in the browser with the native Filereader API is extremely clunky and un-nodelike.
read-blob
fixes that by adding nice errback and Promise interfaces. The data in the blob is buffered into memory and provided as an arraybuffer, base64-encoded data url, or simple text.
If you'd rather not buffer and prefer a streaming interface, check out filereader-stream. In contrast, read-blob
is designed for more simple use-cases where streaming isn't necessary or is simply too much.
If you do not provide a callback, read-blob
will return a Promise. This means that you'll need a Promise implementation in your environment. Either polyfill Promise
, or provide a callback.
npm install --save read-blob
If using require
through something like browserify or webpack is not an option for you, use dist/read-blob.js
from the npm package and it will set readBlob on the global object.
var readBlob = require('read-blob');
readBlob(blob, 'dataurl', function (err, dataurl) {
if (err) throw err;
console.log('that was simple!');
img.src = dataurl;
});
In contrast, using the native FileReader API would look like this:
var reader = new FileReader();
reader.onload = function (res) {
console.log('that was not so simple!');
img.src = dataurl;
}
reader.onend = function (err) {
throw err;
}
reader.onabort = function (err) {
throw err;
}
reader.readAsDataURL(blob);
Ew! Not only is the native API much longer, but it doesn't say what it does, and instead leaks all the procedure of the Filereader API into your program.
Reads the blob data as the given type
. Type can be dataurl
, arraybuffer
, text
, or any text encoding such as 'utf8' (though text
defaults to utf-8 just as it does in native API).
If type
is not provided, it defaults to arraybuffer
.
cb
is a function of the signature function (err, data)
Like the version with cb
, but if no callback function is provided, returns a Promise that resolves to the blob's data in the requested type
.
If type
is not provided, it defaults to arraybuffer
.
readBlob.dataurl(blob)
, readBlob.arraybuffer(blob)
, and readBlob.text(blob)
are all shorthands for reading the blob as the given type.
Combined with their Promise-returning versions, reading a blob becomes quite succinct:
readBlob.dataurl(blob).then(url => # data:image/jpeg;base64,...)