| /*! |
| * fresh |
| * Copyright(c) 2012 TJ Holowaychuk |
| * Copyright(c) 2016-2017 Douglas Christopher Wilson |
| * MIT Licensed |
| */ |
| |
| 'use strict' |
| |
| /** |
| * RegExp to check for no-cache token in Cache-Control. |
| * @private |
| */ |
| |
| var CACHE_CONTROL_NO_CACHE_REGEXP = /(?:^|,)\s*?no-cache\s*?(?:,|$)/ |
| |
| /** |
| * Simple expression to split token list. |
| * @private |
| */ |
| |
| var TOKEN_LIST_REGEXP = / *, */ |
| |
| /** |
| * Module exports. |
| * @public |
| */ |
| |
| module.exports = fresh |
| |
| /** |
| * Check freshness of the response using request and response headers. |
| * |
| * @param {Object} reqHeaders |
| * @param {Object} resHeaders |
| * @return {Boolean} |
| * @public |
| */ |
| |
| function fresh (reqHeaders, resHeaders) { |
| // fields |
| var modifiedSince = reqHeaders['if-modified-since'] |
| var noneMatch = reqHeaders['if-none-match'] |
| |
| // unconditional request |
| if (!modifiedSince && !noneMatch) { |
| return false |
| } |
| |
| // Always return stale when Cache-Control: no-cache |
| // to support end-to-end reload requests |
| // https://tools.ietf.org/html/rfc2616#section-14.9.4 |
| var cacheControl = reqHeaders['cache-control'] |
| if (cacheControl && CACHE_CONTROL_NO_CACHE_REGEXP.test(cacheControl)) { |
| return false |
| } |
| |
| // if-none-match |
| if (noneMatch && noneMatch !== '*') { |
| var etag = resHeaders['etag'] |
| var etagStale = !etag || noneMatch.split(TOKEN_LIST_REGEXP).every(function (match) { |
| return match !== etag && match !== 'W/' + etag && 'W/' + match !== etag |
| }) |
| |
| if (etagStale) { |
| return false |
| } |
| } |
| |
| // if-modified-since |
| if (modifiedSince) { |
| var lastModified = resHeaders['last-modified'] |
| var modifiedStale = !lastModified || Date.parse(lastModified) > Date.parse(modifiedSince) |
| |
| if (modifiedStale) { |
| return false |
| } |
| } |
| |
| return true |
| } |