Non-standard
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
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 is now deprecated as per the 12 July 2012 Working Draft from the W3C.
Syntax
instanceOfFileReader.readAsBinaryString(blob);
Parameters
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.onloadend = function () {
console.log(reader.result);
}
reader.readAsBinaryString(blob);
});
Specifications
This method has been removed from the FileAPI standard. FileReader.readAsArrayBuffer() should be used instead.
Browser compatibility
| Feature | Firefox (Gecko) | Chrome | Edge | Internet Explorer | Opera | Safari |
|---|---|---|---|---|---|---|
| Basic support | 3.6 (1.9.2)[1] | 7 | (Yes) | No support | 12.02[3] | 6.0 |
| Feature | Firefox Mobile (Gecko) | Android | Edge | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|
| Basic support | 32 | 3 | (Yes) | 10 | 11.5 | 6.0 |
[1] Prior to Gecko 2.0 beta 7 (Firefox 4.0 beta 7), all Blob parameters below were File parameters; this has since been updated to match the specification correctly. Prior to Gecko 13.0 (Firefox 13.0 / Thunderbird 13.0 / SeaMonkey 2.10) the FileReader.error property returned a FileError object. This interface has been removed and FileReader.error is now returning the DOMError object as defined in the latest FileAPI draft.
[2] IE9 has a File API Lab.
[3] Opera has partial support in 11.1.