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Encoding/

Encoding

The encoder and decoder are designed based on standard Web APIs TextEncoder and TextDecoder.

TextEncoder

The TextEncoder API takes code point streams as inputs and generates UTF-8 byte streams as outputs. For more information, see TextEncoder.

Constructor API

// The TextEncoder() constructor does not have any parameters.
const encoder = new TextEncoder();

Attributes

// encoder.encoding
readonly encoding: string;
The name of the encoding algorithm that is used by the encoder. The value is fixed to UTF-8.

Methods

encode

encoder.encode(input?: string | undefined): Uint8Array
The encoder.encode() method takes code point streams as inputs and generates UTF-8 byte streams as outputs.
Note:
The maximum length of input is 300 MB. An exception will be thrown if the maximum length is exceeded.
encoder.encode parameters
Parameter
Type
Required
Description
input
string | undefined
No
The text to be encoded.

encodeInto

encoder.encodeInto(input: string, destination: Uint8Array): EncodeIntoResult;
The encoder.encodeInto() method takes code point streams as inputs, generates UTF-8 byte streams as outputs, and writes the outputs to a destination byte array.
Parameters
Parameter
Type
Required
Description
input
string
Yes
The text to be encoded.
destination
Yes
The object in which the encoded text is stored.
Return value: EncodeIntoResult
Parameter
Type
Description
read
number
The number of UTF-16 units that have been converted to UTF-8.
written
number
The number of bytes that are modified in the destination Uint8Array.

TextDecoder

The TextDecoder API takes byte streams as inputs and generates code point streams as outputs. For more information, see TextDecoder.

Construction API

const decoder = new TextDecoder(label?: string | undefined, options?: DecoderOptions | undefined): TextEncoder;

Parameters

Note:
The label parameter does not support the following values:
iso-8859-16
hz-gb-2312
csiso2022kr, iso-2022-kr
Parameter
Type
Required
Description
label
string | undefined
No
The name of the decoding algorithm that is used by the decoder. Default value: UTF-8. For the valid values of label, see Encoding API Encodings.
options
DecoderOptions | undefined
No
The configuration items of the decoder.

DecoderOptions

The following table describes the configuration items of the decoder.
Parameter
Type
Default value
Description
fatal
boolean
false
Specifies whether to throw an exception when decoding fails.
ignoreBOM
boolean
false
Specifies whether to ignore byte-order marker.

Attributes

encoding

// decoder.encoding
readonly encoding: string;
The name of the decoding algorithm that is used by the decoder.

fatal

// decoder.fatal
readonly fatal: boolean;
Specifies whether to throw an exception when decoding fails.

ignoreBOM

// decoder.ignoreBOM
readonly ignoreBOM: boolean;
Specifies whether to ignore byte-order marker.

Methods

decode

const result = decoder.decode(buffer?: ArrayBuffer | ArrayBufferView | undefined, options?: DecodeOptions | undefined): string;
Note:
The maximum length of buffer is 100 MB. An exception will be thrown if the maximum length is exceeded.
Parameter
Type
Required
Description
buffer
No
The byte stream to be decoded.
The maximum length of buffer is 100 MB. An exception will be thrown if the maximum length is exceeded.
options
No
The configuration items for decoding.

DecodeOptions

The following table describes the configuration items for decoding.
Parameter
Type
Default value
Description
stream
boolean
false
Specifies whether to perform decoding in streaming mode. Default value: false. Valid values:
true
Perform decoding in streaming mode. Use this value if data is processed in chunks and additional chunks are expected.
false
Do not perform decoding in streaming mode. Use this value if the current chunk is the last one or data is not chunked.

Sample Code

function handleEvent(event) {
  // Encoder
  const encoder = new TextEncoder();
  const encodeText = encoder.encode('hello world');

  // Decoder
  const decoder = new TextDecoder();
  const decodeText = decoder.decode(encodeText);

  // Response
  const response = new Response(JSON.stringify({
    encodeText: encodeText.toString(),
    decodeText,
  }));

  return response;
}

addEventListener('fetch', (event) => {
  event.respondWith(handleEvent(event));
});

References

MDN documentation: TextEncoder
MDN documentation:TextDecoder
MDN documentation: Encoding API Encodings
Sample Functions: Protecting Data from Tampering