FileReader.readAsBinaryString()

The readAsBinaryString method is used to start reading the contents of the specified Blob or File. When the read operation is finished, the readyState becomes DONE, and the loadend is triggered. At that time, the result attribute contains the raw binary data from the file.

Note that this method was once removed from the File API specification, but re-introduced for backward compatibility.
Using FileReader.readAsArrayBuffer() is recommended.

Syntax

instanceOfFileReader.readAsBinaryString(blob);

Parameters

blob
The Blob or File from which to read.

Example

var canvas = document.createElement('canvas');
var height = 200;
var width  = 200;

canvas.width  = width;
canvas.height = height;

var ctx = canvas.getContext('2d');

ctx.strokeStyle = '#090';
ctx.beginPath();
ctx.arc(width/2, height/2, width/2 - width/10, 0, Math.PI*2);
ctx.stroke();

canvas.toBlob(function (blob) {
  var reader = new FileReader();

  reader.onload = function () {
    console.log(reader.result);
  }

  reader.readAsBinaryString(blob);
});

Specifications

Specification Status Comment
File API
The definition of 'readAsBinaryString' in that specification.
Working Draft

Browser compatibility

BCD tables only load in the browser

See also