method Buffer.copy
Usage in Deno
```typescript import { type Buffer } from "node:node__buffer.d.ts"; ```
Buffer.copy(target: Uint8Array,targetStart?: number,sourceStart?: number,sourceEnd?: number,): number
Copies data from a region of `buf` to a region in `target`, even if the `target`memory region overlaps with `buf`.
[`TypedArray.prototype.set()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/set) performs the same operation, and is available
for all TypedArrays, including Node.js `Buffer`s, although it takes
different function arguments.
```js
import { Buffer } from 'node:buffer';
// Create two `Buffer` instances.
const buf1 = Buffer.allocUnsafe(26);
const buf2 = Buffer.allocUnsafe(26).fill('!');
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'.
buf1[i] = i + 97;
}
// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`.
buf1.copy(buf2, 8, 16, 20);
// This is equivalent to:
// buf2.set(buf1.subarray(16, 20), 8);
console.log(buf2.toString('ascii', 0, 25));
// Prints: !!!!!!!!qrst!!!!!!!!!!!!!
```
```js
import { Buffer } from 'node:buffer';
// Create a `Buffer` and copy data from one region to an overlapping region
// within the same `Buffer`.
const buf = Buffer.allocUnsafe(26);
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'.
buf[i] = i + 97;
}
buf.copy(buf, 0, 4, 10);
console.log(buf.toString());
// Prints: efghijghijklmnopqrstuvwxyz
```
number
The number of bytes copied.