Documentation: http://kailashnadh.name/code/localstoragedb Licensed under the MIT license.
...
// create the "books" table
lib.createTable("books",
["id", "title", "author", "year", "copies"],
["id", "title"] // Add an array as the 3rd parameter with the name of the column that you want to index
);
...
}
After the creation, each insert/update goes also to affect the indexes.
The performances for medium/large data extraction/update from/to your localStorage will raise significantly.
Check this link http://jsperf.com/indexed-localstoragedb/2 to see the performance gain at his best
localStorageDB is a simple layer over localStorage (and sessionStorage) that provides a set of functions to store structured data like databases and tables. It provides basic insert/update/delete/query capabilities. localStorageDB has no dependencies, and is not based on WebSQL. Underneath it all, the structured data is stored as serialized JSON in localStorage or sessionStorage.
- Kailash Nadh
- v 1.9 November 2012
- v 2.0 June 2013
- Documentation: http://nadh.in/code/localstoragedb
- Licensed: MIT license
// Initialise. If the database doesn't exist, it is created
var lib = new localStorageDB("library", localStorage);
// Check if the database was just created. Useful for initial database setup
if( lib.isNew() ) {
// create the "books" table
lib.createTable("books", ["code", "title", "author", "year", "copies"]);
// insert some data
lib.insert("books", {code: "B001", title: "Phantoms in the brain", author: "Ramachandran", year: 1999, copies: 10});
lib.insert("books", {code: "B002", title: "The tell-tale brain", author: "Ramachandran", year: 2011, copies: 10});
lib.insert("books", {code: "B003", title: "Freakonomics", author: "Levitt and Dubner", year: 2005, copies: 10});
lib.insert("books", {code: "B004", title: "Predictably irrational", author: "Ariely", year: 2008, copies: 10});
lib.insert("books", {code: "B005", title: "Tesla: Man out of time", author: "Cheney", year: 2001, copies: 10});
lib.insert("books", {code: "B006", title: "Salmon fishing in the Yemen", author: "Torday", year: 2007, copies: 10});
lib.insert("books", {code: "B007", title: "The user illusion", author: "Norretranders", year: 1999, copies: 10});
lib.insert("books", {code: "B008", title: "Hubble: Window of the universe", author: "Sparrow", year: 2010, copies: 10});
// commit the database to localStorage
// all create/drop/insert/update/delete operations should be committed
lib.commit();
}// simple select queries
lib.query("books", {year: 2011});
lib.query("books", {year: 1999, author: "Norretranders"});
// select all books
lib.query("books");
// select all books published after 2003
lib.query("books", function(row) { // the callback function is applied to every row in the table
if(row.year > 2003) { // if it returns true, the row is selected
return true;
} else {
return false;
}
});
// select all books by Torday and Sparrow
lib.query("books", function(row) {
if(row.author == "Torday" || row.author == "Sparrow") {
return true;
} else {
return false;
}
});// query results are returned as arrays of object literals
// an ID field with the internal auto-incremented id of the row is also included
// thus, ID is a reserved field name
lib.query("books", {author: "ramachandran"});
/* results
[
{
ID: 1,
code: "B001",
title: "Phantoms in the brain",
author: "Ramachandran",
year: 1999,
copies: 10
},
{
ID: 2,
code: "B002",
title: "The tell-tale brain",
author: "Ramachandran",
year: 2011,
copies: 10
}
]
*/// change the title of books published in 1999 to "Unknown"
lib.update("books", {year: 1999}, function(row) {
row.title = "Unknown";
// the update callback function returns to the modified record
return row;
});
// add +5 copies to all books published after 2003
lib.update("books",
function(row) { // select condition callback
if(row.year > 2003) {
return true;
} else {
return false;
}
},
function(row) { // update function
row.year+=5;
return row;
}
);// if there's a book with code B003, update it, or insert it as a new row
lib.insertOrUpdate("books", {code: 'B003'}, { code: "B003",
title: "Freakonomics",
author: "Levitt and Dubner",
year: 2005,
copies: 15});// delete all books published in 1999
lib.deleteRows("books", {year: 1999});
// delete all books published before 2005
lib.deleteRows("books", function(row) {
if(row.year < 2005) {
return true;
} else {
return false;
}
});
lib.commit(); // commit the deletions to localStorage <tr>
<td>tableExists()</td>
<td>table_name</td>
<td>Checks whether a table exists in the database</td>
</tr>
<tr>
<td>createTable()</td>
<td>table_name, fields</td>
<td>Creates a table<br />
- fields is an array of string fieldnames. 'ID' is a reserved fieldname.
</td>
</tr>
<tr>
<td>dropTable()</td>
<td>table_name</td>
<td>Deletes a table from the database</td>
</tr>
<tr>
<td>truncate()</td>
<td>table_name</td>
<td>Empties all records in a table and resets the internal auto increment ID to 0</td>
</tr>
<tr>
<td>rowCount()</td>
<td>table_name</td>
<td>Returns the number of rows in a table</td>
</tr>
<tr>
<td>insert()</td>
<td>table_name, data</td>
<td>Inserts a row into a table and returns its numerical ID<br />
- data is an object literal with field-values<br />
Every row is assigned an auto-incremented numerical ID automatically
</td>
</tr>
<tr>
<td>query()</td>
<td>table_name, query, limit</td>
<td>
Returns an array of rows (object literals) from a table matching the query.<br />
- query is either an object literal or null. If query is not supplied, all rows are returned<br />
- limit is the maximum number of rows to be returned<br />
Every returned row will have it's internal auto-incremented id assigned to the variable ID</td>
</tr>
<tr>
<td>update()</td>
<td>table_name, query, update_function</td>
<td>Updates existing records in a table matching query, and returns the number of rows affected<br />
- query is an object literal or a function. If query is not supplied, all rows are updated<br />
- update_function is a function that returns an object literal with the updated values
</td>
</tr>
<tr>
<td>insertOrUpdate()</td>
<td>table_name, data, query</td>
<td>Inserts a row into a table if the given query matches no results, or updates the rows matching the query.<br />
- query is either an object literal, function, or null.<br />
- data is an object literal with field-values
<br /><br />
Returns the numerical ID if a new row was inserted, or an array of IDs if rows were updated
</td>
</tr>
<tr>
<td>deleteRows()</td>
<td>table_name, query</td>
<td>Deletes rows from a table matching query, and returns the number of rows deleted<br />
- query is either an object literal or a function. If query is not supplied, all rows are deleted
</td>
</tr>
</tbody>
| Method | Arguments | Description |
|---|---|---|
| localStorageDB() | database_name, storage_engine | Constructor - storage_engine can either be localStorage (default) or sessionStorage |
| isNew() | Returns true if a database was created at the time of initialisation with the constructor | |
| drop() | Deletes a database, and purges it from localStorage | |
| tableCount() | Returns the number of tables in a database | |
| commit() | Commits the database to localStorage | |
| serialize() | Returns the entire database as serialized JSON |