Node.js http.validateHeaderValue() Method
The http.validateHeaderValue() (Added in v14.3.0) property is an inbuilt property of the ‘http’ module which performs the low-level validations on the provided value that are done when res.setHeader(name, value) is called.
Passing an illegal value as the value will result in a TypeError being thrown. An undefined value error is identified by code: 'ERR_HTTP_INVALID_HEADER_VALUE'. Invalid value character error is identified by code: 'ERR_INVALID_CHAR'.
It is not necessary to use this method before passing headers to an HTTP request or response. The HTTP module will automatically validate such headers.
Note: Use the latest version of Node.js to get the required Output.
In order to get a response and a proper result, we need to import ‘http’ module.
const http = require('http');
Syntax:
http.validateHeaderValue(name, value);
Parameters: This method accepts two parameters as mentioned above and described below:
- name <String>: It accepts the name of the header and it is case-insensitive.
- value <any>: It accepts any function, array, or string.
Return Value: It does not return any value, instead performs the low-level validations on the provided value.
The below example illustrates the use of http.validateHeaderValue() property in Node.js.
Example 1: Filename: index.js
// Node.js program to demonstrate the
// http.validateHeaderValue() Method
// Importing http module
const http = require('http');
const { validateHeaderValue } = require('http');
// Handling Errors via try-catch
try {
validateHeaderValue('x-my-header', undefined);
} catch (err) {
err instanceof TypeError; // true
// Printing Errors
console.log(& quot;Is undefined Invalid:& quot;,
err.code === 'ERR_HTTP_INVALID_HEADER_VALUE'); // true
// 'Invalid value "undefined" for header "x-my-header"'
console.log(err.message);
}
// Handling Errors via try-catch
try {
http.validateHeaderValue('x-my-header', 'oʊmɪɡə');
} catch (err) {
err instanceof TypeError; // --> true
// Printing Errors
console.log(& quot;Is undefined Invalid:& quot;,
err.code === 'ERR_INVALID_CHAR'); // true
// 'Invalid character in header content ["x-my-header"]'
console.log(err.message);
}
Run the index.js file using the following command:
node index.js
Output:
Is undefined Invalid: true
Invalid value "undefined" for header "x-my-header"
Is undefined Invalid: true
Invalid character in header content ["x-my-header"]
Example 2: Filename: index.js
// Node.js program to demonstrate the
// http.validateHeaderValue() Method
// Importing http module
const http = require('http');
// Another way to import
const { validateHeaderName } = require('http');
// Setting up PORT
const PORT = process.env.PORT || 3000;
// Creating http Server
const httpServer = http.createServer(
function (request, response) {
// Setting up Headers
response.setHeader('Content-Type', 'text/html');
response.setHeader('Set-Cookie',
['type=ninja', 'language=javascript']);
// Handling Errors via try-catch
try {
validateHeaderValue('Content-Type', 'text/html');
} catch (err) {
// false
console.log("Error: ", err instanceof TypeError);
// Printing Errors
console.log(err.message);
}
try {
http.validateHeaderValue('Set-Cookie', ['type=ninja',
'language=javascript']);
} catch (err) {
// false
console.log("Error: ", err instanceof TypeError);
// Printing Errors
console.log(err.message);
}
// Getting the set Headers
const headers = response.getHeaders();
// Printing those headers
console.log(headers);
// Prints Output on the
// browser in response
response.end('ok');
});
// Listening to http Server
httpServer.listen(PORT, () => {
console.log("Server is running at port 3000...");
});
Run the index.js file using the following command:
node index.js
Output:
Output: In-Console
Server is running at port 3000...
Error: false
Valid header...
[Object: null prototype]{
'Content-Type': 'text/html',
'Set-Cookie': ['type=ninja', 'language=javascript']}
Now run http://localhost:3000/ in the browser.
Output: In-Browser
ok
Reference: https://nodejs.org/api/http.html#http_http_validateheadervalue_name_value
