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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

readAsBinaryString(blob)

Parameters

blob: The Blob or File from which to read.

Return value

None (undefined).

Examples

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

Specification
File API # readAsBinaryString

Browser compatibility