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53 lines
1.2 KiB
53 lines
1.2 KiB
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/**
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* Expose `fresh()`.
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*/
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module.exports = fresh;
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/**
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* Check freshness of `req` and `res` headers.
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*
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* When the cache is "fresh" __true__ is returned,
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* otherwise __false__ is returned to indicate that
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* the cache is now stale.
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*
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* @param {Object} req
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* @param {Object} res
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* @return {Boolean}
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* @api public
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*/
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function fresh(req, res) {
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// defaults
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var etagMatches = true;
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var notModified = true;
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// fields
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var modifiedSince = req['if-modified-since'];
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var noneMatch = req['if-none-match'];
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var lastModified = res['last-modified'];
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var etag = res['etag'];
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var cc = req['cache-control'];
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// unconditional request
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if (!modifiedSince && !noneMatch) return false;
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// check for no-cache cache request directive
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if (cc && cc.indexOf('no-cache') !== -1) return false;
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// parse if-none-match
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if (noneMatch) noneMatch = noneMatch.split(/ *, */);
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// if-none-match
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if (noneMatch) etagMatches = ~noneMatch.indexOf(etag) || '*' == noneMatch[0];
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// if-modified-since
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if (modifiedSince) {
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modifiedSince = new Date(modifiedSince);
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lastModified = new Date(lastModified);
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notModified = lastModified <= modifiedSince;
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}
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return !! (etagMatches && notModified);
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}
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