persistent-button

A persistent data structure for storing the history of a toggleable (binary) button. Events in the history are points where the button's state toggles from on to off and vice versa. This data structure supports efficient queries for the amount of time a button is held and how frequently/or whether it is pressed at any point in history.

Example

//Create a button
var createButton = require('persistent-button')
var button = createButton()

//Press button at time t=0.5
button.appendEvent(0.5, true)

//Release button at time t=1
button.appendEvent(1, false)

//Press button again at time t=2
button.appendEvent(2, true)

//Test the button state at different points in history
console.log(button.down(0.75)) //Prints out: true
console.log(button.down(1.5))  //Prints out: false

//Find how many time the button was pressed up to t=3
console.log(button.press(3))  //Prints out: 2

//Print out how long the button was held from beginning of time to t=2.5
console.log(button.hold(2.5)) //Prints out: 1

Install

npm install persistent-button

API

var createButton = require('persistent-button')

Constructor

var button = createButton([history])

Creates a persistent button

• history is an optional history of the button (as created by button.serialize)

Returns A new persistent button object

Methods

button.appendEvent(t, state)

Adds an event to the button's history

• t is the time of the event
• state is the new state of the button (must be either true or false)

button.length

The number of events in the history of the button

button.event(i)

Gives the time of the ith event

• i is the index of the event which is being queries

Returns The time associated to the ith event

button.toggleCount(t)

Counts the number of times the button has been toggled from the beginning of time up to time t

• t is the time which is being queried

Returns The number of times the button has been toggled

button.down(t)

Tests if the button is down at time t

• t is the time to query

Returns true if the button was held down at time t, otherwise false

button.press(t)

Counts the number of time the button has been pressed since the beginning of time.

• t is the query time

Returns The number of times the button has been pressed since the beginning of time and ending at time t

button.release(t)

Counts the number of times the button has been released since the beginning of time.

• t is the query time

Returns The number of times the button has been released since the beginning of time

button.hold(t)

Gives the number of time units that the button has been held since the beginning of time

• t is the query time

Returns How long the button has been held up to time t

button.serialize()

Saves the state of the button to an array for serialization.

Returns An array of times representing the points in history where the button state toggled

button.deserialize(history)

Restores the state of the button from an array of toggle events labeled by time.

• history is an array of toggle events

Credits

(c) 2014 Mikola Lysenko. MIT License