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FileReader: readAsBinaryString() method

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 FileReader.loadend_event 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

js

readAsBinaryString(blob)

Parameters

blob

The Blob or File from which to read.

Return value

None (undefined).

Examples

js

const canvas = document.createElement("canvas");
const height = 200;
const width = 200;

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

const 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((blob) => {
  const reader = new FileReader();

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

  reader.readAsBinaryString(blob);
});

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
readAsBinaryString 6 12 3.6 No 11 6 3 18 32 11 6 1.0

See also

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https://developer.mozilla.org/en-US/docs/Web/API/FileReader/readAsBinaryString