Headers
The Headers API is designed based on the standard Web API Headers. You can use this API to perform operations on HTTP request and response headers.
Constructor API
const headers = new Headers(init?: object | Array<[string, string]> | Headers);
Parameters
Parameter | Type | Required | Description |
init | No | The HTTP header that is used to pre-populate the Headers object. Valid parameter types: object The Constructor API enumerates all enumerable attributes that are included in the specified object and pre-populates the attributes to the new Headers object. Array<[string, string]> Each element in the array is a key-value pair. Example: [key, value]. The Constructor API traverses the array and pre-populates the key-value pairs to the new Headers object. Headers The Constructor API copies all fields from an existing Headers object to the new Headers object. |
Methods
append
headers.append(name: string, value: string): void;
The append() method appends a new value to a header that is specified by the
Headers object. If the header does not exist, the append() method directly adds the header.Note:
The
headers object has the following write-in limits:The name cannot exceed 255 bytes, and can only consist of digits, uppercase and lowercase letters, -, and _. Otherwise, an exception will be thrown.
The value cannot exceed 4,095 bytes. Leading and trailing whitespace characters '\n', '\r', '\t', and ' ' will be automatically removed, and the string cannot contain '\0', '\n', or '\r' in the middle. Otherwise, an exception will be thrown.
Parameters
Parameter | Type | Required | Description |
name | string | Yes | The name of the HTTP header that you want to add to the Headers object. |
value | string | Yes | The value of the HTTP header that you want to add. |
delete
headers.delete(name: string): void;
The delete() method deletes the specified header from the
Headers object.Parameters
Parameter | Type | Required | Description |
name | string | Yes | The name of the HTTP header that you want to delete from the Headers object. |
entries
headers.entries(): iterator;
The entries() method obtains an array of all key-value pairs from the
Headers object. The key-value pairs are in the format of [name, value]. For valid return values, see Iteration protocols.forEach
headers.forEach(callback: (name: string, value: string) => void | number): void;
The forEach() method traverses all headers that are included in the
Headers object. If callback returns a non-zero value, traversal is stopped.Note
The
forEach method does not comply with Web API standards. Edge Functions extends the functionality of the method based on Web API standards to provide an efficient way to traverse headers.get
headers.get(name: string): string;
The get() method obtains the value of the specified header from the
Headers object.getSetCookie
headers.getSetCookie(): Array<string>
has
headers.has(name: string): boolean;
The has() method checks whether the
Headers object contains the specified header.keys
headers.keys(): iterator;
The keys() method obtains all keys that are included in the
Headers object. For valid return values, see Iteration protocols.set
headers.set(name: string, value: string): void;
The set() method sets a new value for an existing header in the
Headers object. If the header does not exist, the set() method directly adds the header.values
headers.values(): iterator;
The values() method obtains all values that are included in the
Headers object. For valid return values, see Iteration protocols.Sample Code
function handleEvent() {const headers = new Headers({'my-header-x': 'hello world',});const response = new Response('hello world',{headers,});return response;}addEventListener('fetch', (event) => {event.respondWith(handleEvent(event));});