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leobetosouza/cache.js

Last active October 5, 2017 15:03
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Simple JS Cache Persistence
Raw
cache.js
window.cache = (function () {
var _data = {};
var _db = openDatabase(
'cache.db',
'1.0',
'app cache database',
5 * 1024 * 1024
)
function executeQuery (query, values, tx) {
values = values || []
return new Promise (resolve, reject) {
var exec = function exec (tx) {
tx.executeSql(
query,
values,
resolve,
reject
)
}
if (tx) {
exec(tx)
} else {
_db.transaction(function (tx) {
exec(tx)
}, reject)
}
}
}
function _save (key) {
if (_data[key] != null) {
return executeQuery(
'INSERT OR REPLACE INTO cache (id, val) VALUES (?, ?);',
[ key, JSON.stringify(_data[key]) ]
)
} else {
return Promise.resolve()
}
}
function _remove (key) {
return executeQuery('DELETE FROM cache WHERE id = ?;', [ key ])
}
function get (key) {
return _data[key];
}
function set (key, val) {
return _save(key).then(function() {
_data[key] = val;
})
}
function del (key) {
return _remove(key).then(function () {
delete _data[key]
})
}
function loadDatabase () {
return executeQuery(
'CREATE TABLE IF NOT EXISTS cache (id TEXT PRIMARY KEY, val TEXT);'
)
.then(function(tx) {
return executeQuery(
'CREATE TABLE IF NOT EXISTS cache (id TEXT PRIMARY KEY, val TEXT);',
[],
tx
)
})
.then(function(tx, res) {
for (var i = 0, l = res.rows.length; i < l; i++) {
_data[res.rows.item(i).id] = JSON.parse(res.rows.item(i).val)
}
})
}
return {
get : get,
set : set,
del : del,
loadDatabase : loadDatabase
}
}())
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