1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
|
// settings.js
// First, let's create a short helper function to get the database connection
function getDatabase() {
return LocalStorage.openDatabaseSync("music-app-settings", "1.0", "StorageDatabase", 1000000);
}
// At the start of the application, we can initialize the tables we need if they haven't been created yet
function initialize() {
var db = getDatabase();
db.transaction(
function(tx) {
// Create the settings table if it doesn't already exist
// If the table exists, this is skipped
//tx.executeSql('DROP TABLE settings');
tx.executeSql('CREATE TABLE IF NOT EXISTS settings(setting TEXT UNIQUE, value TEXT)');
});
}
// This function is used to write a setting into the database
function setSetting(setting, value) {
// setting: string representing the setting name (eg: “username”)
// value: string representing the value of the setting (eg: “myUsername”)
var db = getDatabase();
var res = "";
db.transaction(function(tx) {
var rs = tx.executeSql('INSERT OR REPLACE INTO settings VALUES (?,?);', [setting,value]);
//console.log(rs.rowsAffected)
if (rs.rowsAffected > 0) {
res = "OK";
} else {
res = "Error";
}
}
);
// The function returns “OK” if it was successful, or “Error” if it wasn't
return res;
}
// This function is used to retrieve a setting from the database
function getSetting(setting) {
var db = getDatabase();
var res="";
try {
db.transaction(function(tx) {
var rs = tx.executeSql('SELECT value FROM settings WHERE setting=?;', [setting]);
if (rs.rows.length > 0) {
res = rs.rows.item(0).value;
} else {
res = "Unknown";
}
})
} catch(e) {
return "";
}
// The function returns “Unknown” if the setting was not found in the database
// For more advanced projects, this should probably be handled through error codes
return res
}
|