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