【发布时间】：2017-04-13 16:10:26
【问题描述】：
我有一个函数，如果它存在，它应该从 sessionStorage 返回一个字典，如果不存在，它会将字典从 API 加载到 sessionStorage 然后返回字典。
self.getDictionary = function(dictionary){
var deferred = $q.defer();
var saved_dictionary = JSON.parse($window.sessionStorage.getItem('dictionary_' + dictionary));
if (saved_dictionary && saved_dictionary !== "null"){
deferred.resolve(saved_dictionary);
} else {
var apiData = {module: "Dictionaries", method: "getDictionary", data: {name: dictionary}};
apiService.execute(apiData).then(function (response) {
$window.sessionStorage.setItem('dictionary_' + dictionary, JSON.stringify(response));
deferred.resolve(response);
});
}
return deferred.promise;
};
我正在尝试缓存字典，因为它可能非常大（大约 0.5mb JSON）。
示例字典：
{"DictionaryName":"Gaming","DictionaryCategory":[{"CategoryName":"Games","MandatoryAtLeast":1,"CategoryWords":[{"title":"zelda","score":1,"exact":true,"mandatory":false,"reject":false},{"title":"mass effect","score":1,"exact":false,"mandatory":true,"reject":false},{"title":"pokemon","score":1,"exact":false,"mandatory":true,"reject":false},{"title":"fallout","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"cs:go","score":1,"exact":true,"mandatory":false,"reject":false},{"title":"sims","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"until dawn","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"deus ex","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"skyrim","score":1,"exact":false,"mandatory":true,"reject":false}]},{"CategoryName":"Companies","MandatoryAtLeast":1,"CategoryWords":[{"title":"bioware","score":1,"exact":false,"mandatory":true,"reject":false},{"title":"bethesda","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"steam","score":1,"exact":false,"mandatory":true,"reject":false},{"title":"valve","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"alienware","score":1,"exact":false,"mandatory":false,"reject":false}]},{"CategoryName":"other","MandatoryAtLeast":1,"CategoryWords":[{"title":"gamer","score":1,"exact":false,"mandatory":true,"reject":false},{"title":"mods","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"horror","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"survival","score":1,"exact":true,"mandatory":false,"reject":false},{"title":"multiplayer","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"action","score":1,"exact":true,"mandatory":true,"reject":false},{"title":"fps","score":1,"exact":false,"mandatory":true,"reject":false},{"title":"shooter","score":1,"exact":false,"mandatory":false,"reject":false},{"title":"mmo","score":1,"exact":false,"mandatory":true,"reject":false}]}]}
问题是从缓存中提供字典没有帮助。从 sessionStorage 提供字典所需的时间几乎与从远程 API 加载字典所需的时间一样长。
为什么从 sessionStorage 返回需要这么长时间？
【问题讨论】：
-
为什么在调用
JSON.parse()之前不检查sessionStorage中是否定义了key？ -
我想我可以，但我认为这不会有太大的不同。据我所知，在 null 值上调用 JSON.parse() 可以忽略不计
-
时间有多长？花费的时间会带来什么问题？
-
当你存储数据时，我认为它必须以某种方式被浏览器序列化。我不希望它花费那么长时间，但我的第一个测试仍然是尝试存储少量数据，并从那里进一步得出结论/调试。
-
也不会出现您在检索数据后将数据存储在内存中的情况。一旦它被解析，在作为对象存储在服务中时访问它会快得多
标签： javascript angularjs session-storage