Buffer slice

Learn to slice buffers with Buffer.slice.

Buffer slice

Sometimes you need only part of a buffer. buf.subarray(start, end) returns a view of the buffer: it does not allocate new memory, it shares the original buffer.

For example Buffer.from("hello").subarray(0, 3) gives the first three bytes (hel). start is inclusive, end is exclusive, just like string.slice. In old code you may see buf.slice(), but that method is now deprecated; use subarray instead. Because the view is shared, changes to it also affect the original buffer.

slice is deprecated

In old Node.js code you may see buf.slice(start, end). This method also returns a view like subarray, but it is deprecated. In new code you should use subarray.

Both do the same thing: they return a view that shares the original memory. However, slice may be removed in the future. That is why the official docs recommend subarray. If you see slice while reading old code, just know it means the same as subarray. This way you can understand both old and new code.

Exercise Take a portion of a buffer and print it

Create a buffer with Buffer.from("merhaba"). Take the first three bytes with .subarray(0, 3), convert with .toString() and print with console.log.

Show example solution

console.log(Buffer.from("merhaba").subarray(0, 3).toString());

Test yourself

Complete the subarray call

Buffer.from("merhaba").____(0, 3)

Show answer

Buffer.from("merhaba").subarray(0, 3)

Match each piece to its role

subarray

Returns a view
start

Start index (inclusive)
end

End index (exclusive)
slice

Deprecated
What does Buffer.from("merhaba").subarray(0, 3) return?
```
Buffer.from("merhaba").subarray(0, 3)
```
- "mer"
- "merha"
- "merhaba"
- "rha"
Show answer

"mer" — subarray(0, 3) gives the first three bytes: mer.

Next lesson: Summary - Buffer

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