etag

What is etag?

The etag npm package is used to generate HTTP ETags, which are typically used for cache validation. It can generate ETags based on the contents of a file or a buffer, a string, or based on a specified entity and its attributes.

What are etag's main functionalities?

Generating ETags from a file

This code sample demonstrates how to generate an ETag for the contents of a file. It reads the file 'example.txt' and uses the etag function to create an ETag based on the file's contents.

const etag = require('etag');
const fs = require('fs');

fs.readFile('example.txt', function(err, data) {
  if (err) throw err;
  const eTagValue = etag(data);
  console.log(eTagValue);
});

Generating ETags from a string

This code sample shows how to generate an ETag from a string. The etag function is called with a string 'Hello, World!' to produce an ETag for that specific string.

const etag = require('etag');

const entity = 'Hello, World!';
const eTagValue = etag(entity);
console.log(eTagValue);

Generating ETags with options

This example illustrates how to generate a weak ETag by passing an options object to the etag function. The options object specifies that the ETag should be weak, which is indicated by a 'W/' prefix in the ETag value.

const etag = require('etag');

const entity = Buffer.from('Hello, World!');
const options = { weak: true };
const eTagValue = etag(entity, options);
console.log(eTagValue);

Other packages similar to etag

fresh

The 'fresh' package is used to check if the HTTP response is still 'fresh' on the client side. It is similar to etag in that it deals with HTTP caching mechanisms, but it focuses on cache validation rather than ETag generation.

cacheable-response

The 'cacheable-response' package is a higher-level abstraction for creating cacheable responses in Node.js servers. It uses ETags among other headers to manage caching. It provides a more comprehensive solution compared to etag, which is focused solely on ETag generation.

README

etag

Create simple HTTP ETags

This module generates HTTP ETags (as defined in RFC 7232) for use in HTTP responses.

Installation

This is a Node.js module available through the npm registry. Installation is done using the npm install command:

$ npm install etag

API

var etag = require('etag')

etag(entity, [options])

Generate a strong ETag for the given entity. This should be the complete body of the entity. Strings, Buffers, and fs.Stats are accepted. By default, a strong ETag is generated except for fs.Stats, which will generate a weak ETag (this can be overwritten by options.weak).

res.setHeader('ETag', etag(body))

Options

etag accepts these properties in the options object.

weak

Specifies if the generated ETag will include the weak validator mark (that is, the leading W/). The actual entity tag is the same. The default value is false, unless the entity is fs.Stats, in which case it is true.

Testing

$ npm test

Benchmark

$ npm run-script bench

> etag@1.8.1 bench nodejs-etag
> node benchmark/index.js

  http_parser@2.7.0
  node@6.11.1
  v8@5.1.281.103
  uv@1.11.0
  zlib@1.2.11
  ares@1.10.1-DEV
  icu@58.2
  modules@48
  openssl@1.0.2k

> node benchmark/body0-100b.js

  100B body

  4 tests completed.

  buffer - strong x 258,647 ops/sec ±1.07% (180 runs sampled)
  buffer - weak   x 263,812 ops/sec ±0.61% (184 runs sampled)
  string - strong x 259,955 ops/sec ±1.19% (185 runs sampled)
  string - weak   x 264,356 ops/sec ±1.09% (184 runs sampled)

> node benchmark/body1-1kb.js

  1KB body

  4 tests completed.

  buffer - strong x 189,018 ops/sec ±1.12% (182 runs sampled)
  buffer - weak   x 190,586 ops/sec ±0.81% (186 runs sampled)
  string - strong x 144,272 ops/sec ±0.96% (188 runs sampled)
  string - weak   x 145,380 ops/sec ±1.43% (187 runs sampled)

> node benchmark/body2-5kb.js

  5KB body

  4 tests completed.

  buffer - strong x 92,435 ops/sec ±0.42% (188 runs sampled)
  buffer - weak   x 92,373 ops/sec ±0.58% (189 runs sampled)
  string - strong x 48,850 ops/sec ±0.56% (186 runs sampled)
  string - weak   x 49,380 ops/sec ±0.56% (190 runs sampled)

> node benchmark/body3-10kb.js

  10KB body

  4 tests completed.

  buffer - strong x 55,989 ops/sec ±0.93% (188 runs sampled)
  buffer - weak   x 56,148 ops/sec ±0.55% (190 runs sampled)
  string - strong x 27,345 ops/sec ±0.43% (188 runs sampled)
  string - weak   x 27,496 ops/sec ±0.45% (190 runs sampled)

> node benchmark/body4-100kb.js

  100KB body

  4 tests completed.

  buffer - strong x 7,083 ops/sec ±0.22% (190 runs sampled)
  buffer - weak   x 7,115 ops/sec ±0.26% (191 runs sampled)
  string - strong x 3,068 ops/sec ±0.34% (190 runs sampled)
  string - weak   x 3,096 ops/sec ±0.35% (190 runs sampled)

> node benchmark/stats.js

  stat

  4 tests completed.

  real - strong x 871,642 ops/sec ±0.34% (189 runs sampled)
  real - weak   x 867,613 ops/sec ±0.39% (190 runs sampled)
  fake - strong x 401,051 ops/sec ±0.40% (189 runs sampled)
  fake - weak   x 400,100 ops/sec ±0.47% (188 runs sampled)

License

MIT