Why does modifying a Buffer slice modify the original?

Question

The following modifies a slice of a Buffer.

In doing so, it modifies the original Buffer too. If I were to perform a similar operation on an Array, then the original would remain unchanged.

So is this behavior the result of the specific implementation of the slice method on Node.js' Buffer?

const fs = require('fs');

fs.readFile(__filename, (err, buffer) => {
  const tag = buffer.slice(-2, -1);
  tag[0] = 'B';

  console.log(buffer.toString());
});

 // TAG: A

Wiktor Zychla · Accepted Answer · 2017-06-18 20:15:18Z

2

The docs says

Returns a new Buffer that references the same memory as the original, but offset and cropped by the start and end indices. Note: Modifying the new Buffer slice will modify the memory in the original Buffer because the allocated memory of the two objects overlap.

https://nodejs.org/api/buffer.html#buffer_buf_slice_start_end

answered Jun 18, 2017 at 20:15

Wiktor Zychla

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