Skip to main content
Module

std/encoding/README.md

Deno standard library
denoland/deno_std
Go to Latest
File

encoding

Helper module for dealing with external data structures.

Binary

Implements equivalent methods to Go’s encoding/binary package.

Available Functions:

sizeof(dataType: RawTypes): number
getNBytes(r: Deno.Reader, n: number): Promise<Uint8Array>
varnum(b: Uint8Array, o: VarnumOptions = {}): number | null
varbig(b: Uint8Array, o: VarbigOptions = {}): bigint | null
putVarnum(b: Uint8Array, x: number, o: VarnumOptions = {}): number
putVarbig(b: Uint8Array, x: bigint, o: VarbigOptions = {}): number
readVarnum(r: Deno.Reader, o: VarnumOptions = {}): Promise<number>
readVarbig(r: Deno.Reader, o: VarbigOptions = {}): Promise<bigint>
writeVarnum(w: Deno.Writer, x: number, o: VarnumOptions = {}): Promise<number>
writeVarbig(w: Deno.Writer, x: bigint, o: VarbigOptions = {}): Promise<number>

CSV

API

readMatrix

Parse the CSV from the reader with the options provided and return string[][].

parse

Parse the CSV string/buffer with the options provided. The result of this function is as follows:

  • If you don’t provide opt.skipFirstRow, opt.parse, and opt.columns, it returns string[][].
  • If you provide opt.skipFirstRow or opt.columns but not opt.parse, it returns object[].
  • If you provide opt.parse, it returns an array where each element is the value returned from opt.parse.
ParseOptions
  • skipFirstRow: boolean;: If you provide skipFirstRow: true and columns, the first line will be skipped. If you provide skipFirstRow: true but not columns, the first line will be skipped and used as header definitions.
  • columns: string[] | HeaderOptions[];: If you provide string[] or ColumnOptions[], those names will be used for header definition.
  • parse?: (input: unknown) => unknown;: Parse function for the row, which will be executed after parsing of all columns. Therefore if you don’t provide skipFirstRow, columns, and parse function, input will be string[].
HeaderOptions
  • name: string;: Name of the header to be used as property.
  • parse?: (input: string) => unknown;: Parse function for the column. This is executed on each entry of the header. This can be combined with the Parse function of the rows.
ReadOptions
  • comma?: string;: Character which separates values. Default: ",".
  • comment?: string;: Character to start a comment. Default: "#".
  • trimLeadingSpace?: boolean;: Flag to trim the leading space of the value. Default: false.
  • lazyQuotes?: boolean;: Allow unquoted quote in a quoted field or non double quoted quotes in quoted field. Default: false.
  • fieldsPerRecord?: Enabling the check of fields for each row. If == 0, first row is used as referral for the number of fields.

stringify

  • data is the source data to stringify. It’s an array of items which are plain objects or arrays.

    DataItem: Record<string, unknown> | unknown[]

    const data = [
  {
    name: "Deno",
    repo: { org: "denoland", name: "deno" },
    runsOn: ["Rust", "TypeScript"],
  },
];

  • columns is a list of instructions for how to target and transform the data for each column of output. This is also where you can provide an explicit header name for the column.

    Column:

    • The most essential aspect of a column is accessing the property holding the data for that column on each object in the data array. If that member is at the top level, Column can simply be a property accessor, which is either a string (if it’s a plain object) or a number (if it’s an array).

      const columns = [
  "name",
];

      Each property accessor will be used as the header for the column:

      name
      Deno

    • If the required data is not at the top level (it’s nested in other objects/arrays), then a simple property accessor won’t work, so an array of them will be required.

      const columns = [
  ["repo", "name"],
  ["repo", "org"],
];

      When using arrays of property accessors, the header names inherit the value of the last accessor in each array:

      name org
      deno denoland

    • If the data is not already in the required output format, or a different column header is desired, then a ColumnDetails object type can be used for each column:

      • fn?: (value: any) => string | Promise<string> is an optional function to transform the targeted data into the desired format

      • header?: string is the optional value to use for the column header name

      • prop: PropertyAccessor | PropertyAccessor[] is the property accessor (string or number) or array of property accessors used to access the data on each object

      const columns = [
  "name",
  {
    prop: ["runsOn", 0],
    header: "language 1",
    fn: (str: string) => str.toLowerCase(),
  },
  {
    prop: ["runsOn", 1],
    header: "language 2",
    fn: (str: string) => str.toLowerCase(),
  },
];
      name language 1 language 2
      Deno rust typescript

  • options are options for the delimiter-separated output.

    • headers?: boolean: Whether or not to include the row of headers. Default: true

    • separator?: string: Delimiter used to separate values. Examples:

      • "," comma (Default)
      • "\t" tab
      • "|" pipe
      • etc.

Basic Usage

import { parse } from "https://deno.land/std@0.109.0/encoding/csv.ts";
const string = "a,b,c\nd,e,f";

console.log(
  await parse(string, {
    skipFirstRow: false,
  }),
);
// output:
// [["a", "b", "c"], ["d", "e", "f"]]
import {
  Column,
  stringify,
} from "https://deno.land/std@0.109.0/encoding/csv.ts";

type Character = {
  age: number;
  name: {
    first: string;
    last: string;
  };
};

const data: Character[] = [
  {
    age: 70,
    name: {
      first: "Rick",
      last: "Sanchez",
    },
  },
  {
    age: 14,
    name: {
      first: "Morty",
      last: "Smith",
    },
  },
];

let columns: Column[] = [
  ["name", "first"],
  "age",
];

console.log(await stringify(data, columns));
// first,age
// Rick,70
// Morty,14
//

columns = [
  {
    prop: "name",
    fn: (name: Character["name"]) => `${name.first} ${name.last}`,
  },
  {
    prop: "age",
    header: "is_adult",
    fn: (age: Character["age"]) => String(age >= 18),
  },
];

console.log(await stringify(data, columns, { separator: "\t" }));
// name	is_adult
// Rick Sanchez	true
// Morty Smith	false
//

TOML

This module parse TOML files. It follows as much as possible the TOML specs. Be sure to read the supported types as not every specs is supported at the moment and the handling in TypeScript side is a bit different.

Supported types and handling

:exclamation: Supported with warnings see Warning.

⚠️ Warning

String
  • Regex : Due to the spec, there is no flag to detect regex properly in a TOML declaration. So the regex is stored as string.
Integer

For Binary / Octal / Hexadecimal numbers, they are stored as string to be not interpreted as Decimal.

Local Time

Because local time does not exist in JavaScript, the local time is stored as a string.

Inline Table

Inline tables are supported. See below:

animal = { type = { name = "pug" } }
## Output { animal: { type: { name: "pug" } } }
animal = { type.name = "pug" }
## Output { animal: { type : { name : "pug" } }
animal.as.leaders = "tosin"
## Output { animal: { as: { leaders: "tosin" } } }
"tosin.abasi" = "guitarist"
## Output { tosin.abasi: "guitarist" }
Array of Tables

At the moment only simple declarations like below are supported:

[[bin]]
name = "deno"
path = "cli/main.rs"

[[bin]]
name = "deno_core"
path = "src/foo.rs"

[[nib]]
name = "node"
path = "not_found"

will output:

{
  "bin": [
    { "name": "deno", "path": "cli/main.rs" },
    { "name": "deno_core", "path": "src/foo.rs" }
  ],
  "nib": [{ "name": "node", "path": "not_found" }]
}

Basic usage

import {
  parse,
  stringify,
} from "https://deno.land/std@0.109.0/encoding/toml.ts";
const obj = {
  bin: [
    { name: "deno", path: "cli/main.rs" },
    { name: "deno_core", path: "src/foo.rs" },
  ],
  nib: [{ name: "node", path: "not_found" }],
};
const tomlString = stringify(obj);
console.log(tomlString);

// =>
// [[bin]]
// name = "deno"
// path = "cli/main.rs"

// [[bin]]
// name = "deno_core"
// path = "src/foo.rs"

// [[nib]]
// name = "node"
// path = "not_found"

const tomlObject = parse(tomlString);
console.log(tomlObject);

// =>
// {
//     bin: [
//       { name: "deno", path: "cli/main.rs" },
//       { name: "deno_core", path: "src/foo.rs" }
//     ],
//     nib: [ { name: "node", path: "not_found" } ]
//   }

YAML

YAML parser / dumper for Deno.

Heavily inspired from js-yaml.

Basic usage

parse parses the yaml string, and stringify dumps the given object to YAML string.

import {
  parse,
  stringify,
} from "https://deno.land/std@0.109.0/encoding/yaml.ts";

const data = parse(`
foo: bar
baz:
  - qux
  - quux
`);
console.log(data);
// => { foo: "bar", baz: [ "qux", "quux" ] }

const yaml = stringify({ foo: "bar", baz: ["qux", "quux"] });
console.log(yaml);
// =>
// foo: bar
// baz:
//   - qux
//   - quux

If your YAML contains multiple documents in it, you can use parseAll for handling it.

import { parseAll } from "https://deno.land/std@0.109.0/encoding/yaml.ts";

const data = parseAll(`
---
id: 1
name: Alice
---
id: 2
name: Bob
---
id: 3
name: Eve
`);
console.log(data);
// => [ { id: 1, name: "Alice" }, { id: 2, name: "Bob" }, { id: 3, name: "Eve" } ]

To handle regexp, and undefined types, use the EXTENDED_SCHEMA. Note that functions are no longer supported for security reasons

import {
  EXTENDED_SCHEMA,
  parse,
} from "https://deno.land/std@0.109.0/encoding/yaml.ts";

const data = parse(
  `
  regexp:
    simple: !!js/regexp foobar
    modifiers: !!js/regexp /foobar/mi
  undefined: !!js/undefined ~
# Disabled, see: https://github.com/denoland/deno_std/pull/1275
#  function: !!js/function >
#    function foobar() {
#      return 'hello world!';
#    }
`,
  { schema: EXTENDED_SCHEMA },
);

You can also use custom types by extending schemas.

import {
  DEFAULT_SCHEMA,
  parse,
  Type,
} from "https://deno.land/std@0.109.0/encoding/yaml.ts";

const yaml = "...";
const MyYamlType = new Type("!myYamlType", {
  kind: "sequence",
  /* other type options here*/
});
const MY_SCHEMA = DEFAULT_SCHEMA.extend({ explicit: [MyYamlType] });

parse(yaml, { schema: MY_SCHEMA });

API

parse(str: string, opts?: ParserOption): unknown

Parses the YAML string with a single document.

parseAll(str: string, iterator?: Function, opts?: ParserOption): unknown

Parses the YAML string with multiple documents. If the iterator is given, it’s applied to every document instead of returning the array of parsed objects.

stringify(obj: object, opts?: DumpOption): string

Serializes object as a YAML document.

⚠️ Limitations

  • binary type is currently not stable.

More example

See: https://github.com/nodeca/js-yaml/tree/master/examples

base32

RFC4648 base32 encoder/decoder for Deno.

Basic usage

encode encodes a Uint8Array to RFC4648 base32 representation, and decode decodes the given RFC4648 base32 representation to a Uint8Array.

import {
  decode,
  encode,
} from "https://deno.land/std@0.109.0/encoding/base32.ts";

const b32Repr = "RC2E6GA=";

const binaryData = decode(b32Repr);
console.log(binaryData);
// => Uint8Array [ 136, 180, 79, 24 ]

console.log(encode(binaryData));
// => RC2E6GA=

base64

RFC4648 base64 encoder/decoder for Deno.

Basic usage

encode encodes a Uint8Array to RFC4648 base64 representation, and decode decodes the given RFC4648 base64 representation to a Uint8Array.

import {
  decode,
  encode,
} from "https://deno.land/std@0.109.0/encoding/base64.ts";

const b64Repr = "Zm9vYg==";

const binaryData = decode(b64Repr);
console.log(binaryData);
// => Uint8Array [ 102, 111, 111, 98 ]

console.log(encode(binaryData));
// => Zm9vYg==

base64url

RFC4648 base64url encoder/decoder for Deno.

Basic usage

encode encodes a Uint8Array to RFC4648 base64url representation, and decode decodes the given RFC4648 base64url representation to a Uint8Array.

import {
  decode,
  encode,
} from "https://deno.land/std@0.109.0/encoding/base64url.ts";

const binary = new TextEncoder().encode("foobar");
const encoded = encode(binary);
console.log(encoded);
// => "Zm9vYmFy"

console.log(decode(encoded));
// => Uint8Array(6) [ 102, 111, 111, 98, 97, 114 ]

ascii85

Ascii85/base85 encoder and decoder with support for multiple standards.

Basic usage

encode encodes a Uint8Array to a ascii85 representation, and decode decodes the given ascii85 representation to a Uint8Array.

import {
  decode,
  encode,
} from "https://deno.land/std@0.109.0/encoding/ascii85.ts";

const a85Repr = "LpTqp";

const binaryData = decode(a85Repr);
console.log(binaryData);
// => Uint8Array [ 136, 180, 79, 24 ]

console.log(encode(binaryData));
// => LpTqp

Specifying a standard and delimiter

By default all functions are using the most popular Adobe version of ascii85 and not adding any delimiter. However, there are three more standards supported - btoa (different delimiter and additional compression of 4 bytes equal to 32), Z85 and RFC 1924. It’s possible to use a different encoding by specifying it in options object as a second parameter.

Similarly, it’s possible to make encode add a delimiter (<~ and ~> for Adobe, xbtoa Begin and xbtoa End with newlines between the delimiters and encoded data for btoa. Checksums for btoa are not supported. Delimiters are not supported by other encodings.)

encoding examples:

import {
  decode,
  encode,
} from "https://deno.land/std@0.109.0/encoding/ascii85.ts";
const binaryData = new Uint8Array([136, 180, 79, 24]);
console.log(encode(binaryData));
// => LpTqp
console.log(encode(binaryData, { standard: "Adobe", delimiter: true }));
// => <~LpTqp~>
console.log(encode(binaryData, { standard: "btoa", delimiter: true }));
/* => xbtoa Begin
LpTqp
xbtoa End */
console.log(encode(binaryData, { standard: "RFC 1924" }));
// => h_p`_
console.log(encode(binaryData, { standard: "Z85" }));
// => H{P}{

hex

hexadecimal encoder/decoder for Deno.

Basic usage

encode encodes a Uint8Array to hexadecimal Uint8Array with 2 * length, and decode decodes the given hexadecimal Uint8Array to a Uint8Array.

import {
  decode,
  encode,
} from "https://deno.land/std@0.109.0/encoding/hex.ts";

const binary = new TextEncoder().encode("abc");
const encoded = encode(binary);
console.log(encoded);
// => Uint8Array(6) [ 54, 49, 54, 50, 54, 51 ]

console.log(decode(encoded));
// => Uint8Array(3) [ 97, 98, 99 ]