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February 5, 2023 16:23
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Simple in-memory JavaScript object cache with a maxAge per key (in seconds) and maxEntries limit (per cache instance).
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var MemoryCache = function (options) { | |
options = $.extend(true, { | |
maxEntries: null | |
}, options || {}); | |
var self = this; | |
var cache = {}; | |
var entries = 0; | |
var ageOf = function (entry) { | |
return Math.round((new Date() - entry.setAt) / 1000); | |
}; | |
var deleteEntryByKey = function (key) { | |
delete cache[key]; | |
if (entries > 0) entries--; | |
}; | |
var deleteOldestEntry = function () { | |
var keyOfOldestItem, dateOfOldestItem; | |
for (var key in cache) { | |
if (!dateOfOldestItem || dateOfOldestItem > cache[key].setAt) { | |
dateOfOldestItem = cache[key].setAt; | |
keyOfOldestItem = key; | |
} | |
} | |
if (keyOfOldestItem) { | |
deleteEntryByKey(keyOfOldestItem); | |
} | |
}; | |
self.set = function (key, value, maxAge) { | |
if (cache[key]) { | |
cache[key].value = value; | |
cache[key].setAt = new Date(); | |
cache[key].maxAge = maxAge || cache[key].maxAge; | |
} else { | |
if (options.maxEntries && entries >= options.maxEntries) { | |
deleteOldestEntry(); | |
} | |
cache[key] = { | |
value: value, | |
setAt: new Date(), | |
maxAge: maxAge | |
}; | |
entries++; | |
} | |
}; | |
self.get = function (key) { | |
var entry = cache[key]; | |
if (entry) { | |
if (entry.maxAge && entry.maxAge <= ageOf(entry)) { | |
deleteEntryByKey(key); | |
} | |
return entry.value; | |
} | |
}; | |
}; |
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