value-collection

A collection of types and utility functions for manipulating case-insensitive maps of values, such as HTTP headers.

API

ValueCollection

interface ValueCollection<T> {
  [key: string]: T;
}

A key-value map.

addToValues()

function addToValues<T>(values: T[] | T | undefined, value: T): T[] | T;

Adds value to the end of the values array, returning a new instead of modifying the original.

addValue()

function addValue<T>(
  values: ValueCollection<T[]>,
  key: string,
  value: T,
): ValueCollection<T[]>;
function addValue<T>(
  values: ValueCollection<T | T[]>,
  key: string,
  value: T,
): ValueCollection<T | T[]>;

Adds a value to a key, which may or may not already exist.

findKey()

function findKey<T>(
  headers: ValueCollection<T>,
  key: string,
): string | undefined;

Does a case-insensitive search for a key and returns the original case or undefined if not found.

getLastValue()

function getLastValue<T>(
  values: ValueCollection<T | T[]>,
  key: string,
): T | undefined;
function getLastValue<T>(
  values: ValueCollection<T[]>,
  key: string,
): T | undefined;

Get the last value for a given key in a map of arrays.

getValue()

function getValue<T>(values: ValueCollection<T>, key: string): T | undefined;

Does a case-insensitive search for a key and returns the value if it exists.

normalize()

function normalize<T>(values: ValueCollection<T[]>): ValueCollection<T | T[]>;

For a map with array values, returns the result of calling normalizeValue() to each value, removing undefined values.

normalizeValue()

function normalizeValue<T>(value: T[]): T | T[] | undefined;

If value has zero elements, return undefined; if value has 1 element, return the element; and otherwise return the array.

overrideValues()

function overrideValues<T>(
  ...collections: ValueCollection<T>[]
): ValueCollection<T>;

Process the collections from left to right, with later values overriding earlier ones.

setValue()

function setValue<T>(
  values: ValueCollection<T>,
  key: string,
  value: T,
): ValueCollection<T>;

Set a value in a collection with a case-insensitive key lookup.

toArrayValue()

function toArrayValue<T>(value: T | T[]): T[];

Ensure that value is an array.

toArrayValues()

function toArrayValues<T>(
  values: ValueCollection<T | T[]>,
): ValueCollection<T[]>;

Convert each value in the map into an array.