CODEWITHSUNDEEP
javascriptnode.js
Ben Aston
Ben Aston

Reputation: 55739

Why does modifying a Buffer slice modify the original?

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

Upvotes: 0

Views: 353

Answers (1)

Wiktor Zychla
Wiktor Zychla

Reputation: 48240

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

Upvotes: 2

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