bitArray.js

A simple, well commented, pure Javascript implementation of a bit array for storing and manipulating boolean values.

Why should I use this?

This library is being developed in order to provide javascipt developers with an intuitue, simple API to store a large number of boolean (true/false) values with minimal overhead. Accessing values and changing them are all constant in their time complexity (excluding the 'trueBits' and 'percentTrue' methods). Under the hood, this library uses bitwise operations on unsigned 8 bit integers, so it's memory and processor consumtion is at an absolute minimum.

What are some usage cases?

Originally this library was developed to assist with a learning repo, LearnBloomFilters, which is a testing driven repo to help javascript developers create a bloom filter implementation. To implement a bloom filter well, the developer requries a high performance way to manipulate a large array of boolean values, so this library was an answer to that requirement. Although it excels in this function, it is suitable to act as a boolean array where vanilla javascript is the required platform.

How do I use it?

First, the developer needs to instantiate a new BitArray object using the new operator and calling the BitArray constructor, passing in the desired length of the array as the only parameter.

var ba = new BitArray(100);

Now you have a bit array! By default, every bit in the array is set to 0 (false). To turn on a bit in the array, simply call the flipOn method and pass in the desired index you would like to set to 1 (true).

ba.flipOn(50);

To turn a bit off, whether or not it is off or on, simply use the flipOff method (and be sure to apologize to the bit for your rude behavior after). It needs only the desired index as a parameter.

ba.flipOff(50);

The bit array has a method toggle, which will turn on a bit that's off, or turn off a bit that's on. It takes one parameter, which is the index the developer would like to toggle.

ba.toggle(50);

If you would like to determine the value of a bit at a given index, simply call the check method on the BitArray object and pass in the index you are curious about.

ba.check(50);
\\ returns true;
ba.check(75);
\\ returns false;

The BitArray object also has a method for determining the amount of bits that are true in the array relative to the total length of the array. This method is called percentTrue.

ba.percentTrue();
\\ returns .01