localStorageDB 2.3.2

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 2.3.2 Mar 2018 Contribution: Ken Kohler
• v 2.3.1 Mar 2015
• v 2.3.0 Feb 2014 Contribution: Christian Kellner (http://orange-coding.net)
• v 2.2 Jan 2014 Contribution: Andy Hawkins (http://a904guy.com)
• v 2.1 Nov 2013
• v 2.0 Jun 2013
• v 1.9 Nov 2012
• Documentation: http://nadh.in/code/localstoragedb
• Licensed: MIT license

Installation

NPM

npm install localstoragedb

Yarn

yarn install localstoragedb

Bower

bower install localstoragedb

Run Test Cases

bower install # install mocha and chai for running test cases

open test/local_storage_db_test.html in Browser to check the result

Supported Browsers

Browsers need to support "Local Storage" in order to make localeStorageDB working.

• IE 8<
• Firefox 31<
• Chrome 31<
• Safari 7<
• iOS Safari 7.1<
• Android Browser 4.1<
• Chrome for Android 42<

Usage / Examples

Creating a database, table, and populating the table

// 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();
}

Creating and populating a table in one go

	// rows for pre-population
	var rows = [
		{code: "B001", title: "Phantoms in the brain", author: "Ramachandran", year: 1999, copies: 10},
		{code: "B002", title: "The tell-tale brain", author: "Ramachandran", year: 2011, copies: 10},
		{code: "B003", title: "Freakonomics", author: "Levitt and Dubner", year: 2005, copies: 10},
		{code: "B004", title: "Predictably irrational", author: "Ariely", year: 2008, copies: 10},
		{code: "B005", title: "Tesla: Man out of time", author: "Cheney", year: 2001, copies: 10},
		{code: "B006", title: "Salmon fishing in the Yemen", author: "Torday", year: 2007, copies: 10},
		{code: "B007", title: "The user illusion", author: "Norretranders", year: 1999, copies: 10},
		{code: "B008", title: "Hubble: Window of the universe", author: "Sparrow", year: 2010, copies: 10}
	];

	// create the table and insert records in one go
	lib.createTableWithData("books", rows);

	lib.commit();

Altering

// If database already exists, and want to alter existing tables
if(! (lib.columnExists("books", "publication")) ) {
	lib.alterTable("books", "publication", "McGraw-Hill Education");
	lib.commit(); // commit the deletions to localStorage
}

// Multiple columns can also added at once
if(! (lib.columnExists("books", "publication") && lib.columnExists("books", "ISBN")) ) {
	lib.alterTable("books", ["publication", "ISBN"], {publication: "McGraw-Hill Education", ISBN: "85-359-0277-5"});
	lib.commit(); // commit the deletions to localStorage
}

Querying

query() is deprecated. Use queryAll() instead.

// simple select queries
lib.queryAll("books", {
	query: {year: 2011}
});
lib.queryAll("books", {
	query: {year: 1999, author: "Norretranders"}
});

// select all books
lib.queryAll("books");

// select all books published after 2003
lib.queryAll("books", {
	query: 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.queryAll("books", {
    query: function(row) {
            if(row.author == "Torday", row.author == "Sparrow") {
		        return true;
	        } else {
		        return false;
	    }
    },
    limit: 5
});

Sorting

// select 5 rows sorted in ascending order by author
lib.queryAll("books", { limit: 5,
                        sort: 
                      });

// select all rows first sorted in ascending order by author, and then, in descending, by year
lib.queryAll("books", { sort: [["author", "ASC"], ["year", "DESC"]] });

lib.queryAll("books", { query: {"year": 2011},
                        limit: 5,
                        sort: 
                      });

// or using query()'s positional arguments, which is a little messy (DEPRECATED)
lib.query("books", null, null, null, );

Distinct records

lib.queryAll("books", { distinct: ["year", "author"]
                      });

Example results from a query

// 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.queryAll("books", {query: {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
 }
]
*/

Updating

// 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.copies+=5;
		return row;
	}
);

Insert or Update conditionally

// 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});

lib.commit();

Deleting

// 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

Methods

Storing complex objects

While the library is meant for storing fundamental types (strings, numbers, bools), it is possible to store object literals and arrays as column values, with certain caveats. Some comparison queries, distinct etc. may not work. In addition, if you retrieve a stored array in a query result and modify its values in place, these changes will persist throughout further queries until the page is refreshed. This is because localStorageDB loads and unserializes data and keeps it in memory in a global pool until the page is refreshed, and arrays and objects returned in results are passed by reference.

If you really need to store arrays and objects, you should implement a deep-copy function through which you pass the results before manipulation.