JavaScript Local Database - create and manipulate a type safe JavaScript object database. Lives in memory, saves to JSON.

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Glossary of terms used in this document


const jsldb = require('jsldb')

jsldb.connect(dbName, tableSchemas)

param type desc
dbName string The significance of this string is the db file name upon calling save() or saveSync(). The file will be saved as dbName.db.json in the current directory
tableSchemas Schema This object configures the field and type data.

Adding Entries

db.insert(table, entry, callback)

param type desc
table string The name of the table the new entry will be inserted into. This is the same as its key in the Schema in quotes.
entry object The entry (conforming to the table’s schema) that will be inserted. It will be assigned an _id automatically.
callback function (Error, entry) The entry parameter will, on success, be the entry passed to the insert function with its newly-minted _id field.
db.insert('table', entry, (err, entry) => {
    if (err) res.redirect('/failure')
    if (entry) res.redirect('/success')

Deleting Entries

db.deleteById(table, id, callback)

param type desc
table string The table to select
id UUID string The id of the item to delete
callback function (Error)
db.deleteById('table', entry._id, handleDelete)

Updating Entries

db.updateById(table, id, callback)

param type desc
table string The table to select
id UUID string The id of the item to delete
callback function (Error, entry) REQUIRED

Make the changes to the entry inside of the callback

db.updateById('table', uuid, (err, entry) => {
    if (err) res.redirect('/failure')
    entry.name = 'new name'
const updateEntry = (err, entry) => {
    if (err) res.redirect('/failure')
    entry.name = 'new name'

db.updateById('table', entry._id, updateEntry)

be sure to call .save() on the entry, otherwise nothing will happen.


db.saveSync() -> Boolean

Returns true if writing the file succeeds.

if (db.saveSync()) res.redirect('/success')
else res.redirect('/failure')


Callback (Error) => { ... }

db.save((err) => {
    if (err) res.redirect('/failure', { error: err })
    else res.redirect('/success')

Handle fs.write error inside the callback.


The search process consists of Query passed to a find function. Before submitting a query, consider the conditions and then insert those parameters into a new query.

new Query(table, field, logic, value)

param type desc
table string The table to select
field string The field to check
logic string A Query Logic string

Query Logic

When constructing a a query, you may choose from the following logic:

string desc
'eq' strict equal to
'gt' greater than (literally value > entry ?)
'lt' less than
'gte' greater than or equal to
'lte' less than or equal to
'regex' new RegExp('/something/g')
'contains' for array fields only, does the array contain?

For each of the boolean comparisons above, it is literally value > entry ? ...

const q = new Query('table', 'field', 'lte', 64)

See Queries for more detail.

Find Functions

find(query, options, callback) -> entries: object

param members type default desc
query   Query or Query[]    
options   'object'    
  .queryLogic 'string' ALL The type of logic used when combining multiple queries. Accepted values are 'AND' and 'OR'
  .n 'number' Infinity The number of matching entries to return
callback   'function'   (err, entries)

This is the main find function. All others are simply mapped to this functions for convenience. You may omit the options object and pass (query, callback) as the parameters. You will get the defaults in the table above.

Entries will be null, or 1+ entries as an object with ._id as keys.

    new Query('table1', 'size', 'gt', 5),
    new Query('table1', 'size')
], (err, entries) => {
    if (err) res.redirect('/failure')
    if (entries) res.redirect('/success', { entries: entries })

Basic find functions

All of these functions have the parameters (query, callback) where query is Query or Query[], and the callback gets (err, entries).

(query, callback)

function logic
findAll AND Logic
findAny OR Logic
findAny1 OR Logic
find1 AND Logic
findAny(new Query('table', 'age', 'lt', 50),
    (err, entries) => {
        if (err) res.redirect('/failure')
        if (entries) res.redirect('/success')

Find N functions

Find n functions work the same as other find functions, but require an additional parameter.

(n, query, callback)

function logic
findN AND
findAnyN OR
db.findN(5, new Query('table', 'length', 'gt', 100),
    (err, entries) => {


Most of the callbacks have two parameters

  1. Instance of Error if there was one, otherwise null
  2. The entry or entries in question. This is dependent upon the context, see the function in question for more info.

All callback parameters are optional. In some instances, though, the method requires a callback.


const foundEntry = db.findOne(new Query('table', 'field', 'eq', val))
if (foundEntry) {
    res.render('somePage', { entry: foundEntry })


    new Query('table', 'field', 'eq', val),
    (err, entry) => {
        if (err) res.redirect('/failure')
        if (entry) res.render('somePage', { entry: entry })


const newEntry = db.insert('table', entry)
const query = new Query('table', 'group', 'eq', 'name-of-group')
// This is how updating works. You have to get to the _id (the UUID)
const otherEntriesl = db.find(query)
db.updateByIds('table', otherEntry._id, (err, entry) => {
    if (err) res.redirect('/failure')


db.insert('table', entry, (err, newEntry) => {
        new Query('table', 'group', 'eq', 'name-of-group'),
        { queryType: 'AND' },
        (err, entries) => {
            if (err) {
            for (var id in entries) {

Sometimes a callback is convenient. Other times, like the last example above, it can get really deep, really fast. Callback hell.

Any time this happens, refactor your code. Remember, for virtually all functions (except updateById) the callback parameter is optional. It is for convenience. The function also returns the entry or an error.


Raw data

There are getters for a few raw data members:

db.tables() -> the complete raw tables object

db.schema() -> the verified schema object

db.path() -> path to the .db.json file