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# String Decoder#

Stability: 2 - Stable

The `string_decoder` module provides an API for decoding `Buffer` objects into strings in a manner that preserves encoded multi-byte UTF-8 and UTF-16 characters. It can be accessed using:

    const { StringDecoder } = require('string_decoder');

The following example shows the basic use of the `StringDecoder` class.

    const { StringDecoder } = require('string_decoder');
    const decoder = new StringDecoder('utf8');

    const cent = Buffer.from([0xC2, 0xA2]);
    console.log(decoder.write(cent));

    const euro = Buffer.from([0xE2, 0x82, 0xAC]);
    console.log(decoder.write(euro));

When a `Buffer` instance is written to the `StringDecoder` instance, an internal buffer is used to ensure that the decoded string does not contain any incomplete multibyte characters. These are held in the buffer until the next call to `stringDecoder.write()` or until `stringDecoder.end()` is called.

In the following example, the three UTF-8 encoded bytes of the European Euro symbol (`€`) are written over three separate operations:

    const { StringDecoder } = require('string_decoder');
    const decoder = new StringDecoder('utf8');

    decoder.write(Buffer.from([0xE2]));
    decoder.write(Buffer.from([0x82]));
    console.log(decoder.end(Buffer.from([0xAC])));

## Class: new StringDecoder([encoding])#

Added in: v0.1.99

- `encoding` <string> The character encoding the `StringDecoder` will use. Defaults to `'utf8'`.

Creates a new `StringDecoder` instance.

### stringDecoder.end([buffer])#

Added in: v0.9.3

- `buffer` <Buffer> A `Buffer` containing the bytes to decode.

Returns any remaining input stored in the internal buffer as a string. Bytes representing incomplete UTF-8 and UTF-16 characters will be replaced with substitution characters appropriate for the character encoding.

If the `buffer` argument is provided, one final call to `stringDecoder.write()` is performed before returning the remaining input.

### stringDecoder.write(buffer)#

History

Version | Changes
--- | ---
v8.0.0 | Each invalid character is now replaced by a single replacement character instead of one for each individual byte.
v0.1.99 | Added in: v0.1.99

- `buffer` <Buffer> A `Buffer` containing the bytes to decode.

Returns a decoded string, ensuring that any incomplete multibyte characters at the end of the `Buffer` are omitted from the returned string and stored in an internal buffer for the next call to `stringDecoder.write()` or `stringDecoder.end()`.