How can I console.log() a Blob object?

Question

I have a Blob object I want to inspect by logging its value. All I can see are type and size properties. Is there a way to do this?

Goniometer

What browser are you using? – Featherweight

I'm using Chrome 39 (latest as of now) – Goniometer

You cannot directly view the data inside a blob object, you have to use something like FileReader's readDataAs* methods – Konstanze

Answer 1

Updated for 2023, this can now be done with

await blob.text()

(Thanks @Kaiido)

Goniometer

Answer 2

Basic example on using a FileReader to look at the content in a blob

var html= ['<a id="anchor">Hello World</a>'];
var myBlob = new Blob(html, { type: 'text/xml'});
var myReader = new FileReader();
myReader.onload = function(event){
    console.log(JSON.stringify(myReader.result));
};
myReader.readAsText(myBlob);

Hymnal

Can be utterly shortened with await blob.text() nowadays. – Barbey

@Barbey thanks for that updated answer - I've just posted that and changed the accepted answer. – Goniometer

Answer 3

First of all we should create a function for converting blob to base64:

const blobToBase64 = blob => {
  const reader = new FileReader();
  reader.readAsDataURL(blob);
  return new Promise(resolve => {
    reader.onloadend = () => {
      resolve(reader.result);
    };
  });
};

Then we can use this function to use it for console.log:

blobToBase64(blobData).then(res => {
  console.log(res); // res is base64 now
  // even you can click on it to see it in a new tab
});

Lanlana

He did not want to see base64. – Farci