FileReader: readAsBinaryString() method

Deprecated

Avoid using this feature in new projects. This feature may be a candidate for removal from web standards or browsers.

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Note: This feature is available in Web Workers.

Note: This method is deprecated in favor of readAsArrayBuffer().

The readAsBinaryString() method of the FileReader interface is used to start reading the contents of the specified Blob or File. When the read operation is finished, the readyState property becomes DONE, and the loadend event is triggered. At that time, the result property 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 = "#009900";
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);
});