Vary

Summary

The value of a Vary HTTP header.

The Vary header indicates which request headers affect whether a cached response can be used, enabling proper content negotiation caching.

Header names are normalized to lowercase for case-insensitive comparison.

MDN Vary Reference

HTTP/1.1 Specification

Signature

class Vary {
  constructor(init: string | string[] | VaryInit): Vary;

  // Accessors
  get headerNames(): string[];
  get size(): number;

  // Methods
  [iterator](): IterableIterator<string>;
  add(headerName: string): void;
  clear(): void;
  delete(headerName: string): void;
  forEach(
    callback: (headerName: string, vary: Vary) => void,
    thisArg: any,
  ): void;
  has(headerName: string): boolean;
  toString(): string;
  from(value: string | string[] | VaryInit | null): Vary;
}

Accessors

headerNames

An array of the header names (normalized to lowercase).

size

The number of header names in the Vary header.

Methods

[iterator](): IterableIterator<string>

Iterates over normalized header names in the Vary set.

add(headerName: string): void

Adds a header name to the Vary header (case-insensitive). If the header name already exists, this is a no-op.

Parameters

headerName

The header name to add.

clear(): void

Removes all header names from the Vary header.

delete(headerName: string): void

Removes a header name from the Vary header (case-insensitive).

Parameters

headerName

The header name to remove.

forEach(callback: (headerName: string, vary: Vary) => void, thisArg: any): void

Calls a callback function for each header name in the Vary header.

Parameters

callback

The callback function to call for each header name.

thisArg

Optional value to use as this when executing the callback.

has(headerName: string): boolean

Checks if the Vary header includes the given header name (case-insensitive).

Parameters

headerName

The header name to check for.

toString(): string

Returns the serialized Vary header value.

from(value: string | string[] | VaryInit | null): Vary

Parse a Vary header value.

Parameters

value

The header value (string, string[], init object, or null)