# etag [![NPM Version][npm-image]][npm-url] [![NPM Downloads][downloads-image]][downloads-url] [![Node.js Version][node-version-image]][node-version-url] [![Build Status][travis-image]][travis-url] [![Test Coverage][coveralls-image]][coveralls-url] 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](https://nodejs.org/en/) module available through the [npm registry](https://www.npmjs.com/). Installation is done using the [`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally): ```sh $ npm install etag ``` ## API ```js 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, `Buffer`s, 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`). ```js 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 ```sh $ npm test ``` ## Benchmark ```bash $ npm run-script bench > etag@1.8.0 bench nodejs-etag > node benchmark/index.js http_parser@2.7.0 node@6.9.1 v8@5.1.281.84 uv@1.9.1 zlib@1.2.8 ares@1.10.1-DEV icu@57.1 modules@48 openssl@1.0.2j > node benchmark/body0-100b.js 100B body 4 tests completed. * buffer - strong x 498,600 ops/sec ±0.82% (191 runs sampled) * buffer - weak x 496,249 ops/sec ±0.59% (179 runs sampled) string - strong x 466,298 ops/sec ±0.88% (186 runs sampled) string - weak x 464,298 ops/sec ±0.84% (184 runs sampled) > node benchmark/body1-1kb.js 1KB body 4 tests completed. * buffer - strong x 346,535 ops/sec ±0.32% (189 runs sampled) * buffer - weak x 344,958 ops/sec ±0.52% (185 runs sampled) string - strong x 259,672 ops/sec ±0.82% (191 runs sampled) string - weak x 260,931 ops/sec ±0.76% (190 runs sampled) > node benchmark/body2-5kb.js 5KB body 4 tests completed. * buffer - strong x 136,510 ops/sec ±0.62% (189 runs sampled) * buffer - weak x 136,604 ops/sec ±0.51% (191 runs sampled) string - strong x 80,903 ops/sec ±0.84% (192 runs sampled) string - weak x 82,785 ops/sec ±0.50% (193 runs sampled) > node benchmark/body3-10kb.js 10KB body 4 tests completed. * buffer - strong x 78,650 ops/sec ±0.31% (193 runs sampled) * buffer - weak x 78,685 ops/sec ±0.41% (193 runs sampled) string - strong x 43,999 ops/sec ±0.43% (193 runs sampled) string - weak x 44,081 ops/sec ±0.45% (192 runs sampled) > node benchmark/body4-100kb.js 100KB body 4 tests completed. buffer - strong x 8,860 ops/sec ±0.66% (191 runs sampled) * buffer - weak x 9,030 ops/sec ±0.26% (193 runs sampled) string - strong x 4,838 ops/sec ±0.16% (194 runs sampled) string - weak x 4,800 ops/sec ±0.52% (192 runs sampled) > node benchmark/stats.js stat 4 tests completed. * real - strong x 1,468,073 ops/sec ±0.32% (191 runs sampled) * real - weak x 1,446,852 ops/sec ±0.64% (190 runs sampled) fake - strong x 635,707 ops/sec ±0.33% (194 runs sampled) fake - weak x 627,708 ops/sec ±0.36% (192 runs sampled) ``` ## License [MIT](LICENSE) [npm-image]: https://img.shields.io/npm/v/etag.svg [npm-url]: https://npmjs.org/package/etag [node-version-image]: https://img.shields.io/node/v/etag.svg [node-version-url]: https://nodejs.org/en/download/ [travis-image]: https://img.shields.io/travis/jshttp/etag/master.svg [travis-url]: https://travis-ci.org/jshttp/etag [coveralls-image]: https://img.shields.io/coveralls/jshttp/etag/master.svg [coveralls-url]: https://coveralls.io/r/jshttp/etag?branch=master [downloads-image]: https://img.shields.io/npm/dm/etag.svg [downloads-url]: https://npmjs.org/package/etag