ts-fifo-array

A fixed-length, first-in-first-out array for Javascript.

This is a TypeScript/ES6 rewrite of fifo-array.

fifo-array is a great simple module but its missing its type definitions and hasnt been updated for many years so easiest to just copy-paste-and-update it.

This is a drop-in replacement for fifo-array and thanks to good unit tests on the original project its easy to test correct behaviour of this updated version and reuse the documentation.

All credit to Ben Bradley for writing the original.

Install

npm install ts-fifo-array

Methods

All FifoArray methods behave exactly like the Array.prototype methods, but they trim the array down to have a length equal to the max. Which end of the array that is trimmed is the difference:

• FifoArray.push() - Trims from the front of the array until length === max.
• FifoArray.unshift() - Trims from the back of the array until length === max.
• FifoArray.splice() - Trims from the back of the array until length === max.

All other Array.prototype methods are untouched and will behave as expected. I couldn't find any other methods that could add elements to the FifoArray

Examples

Basic usage

import TsFifoArray from "ts-fifo-array"

const fifoArray = TsFifoArray(3, [ 'a', 'b', 'c', 'd' ]);
console.log(fifoArray); // => [ 'b', 'c', 'd' ]
console.log('max:', fifoArray.max); // => max: 3
fifoArray.push(1, 2);
console.log(fifoArray); // => [ 'd', 1, 2 ]

#push()

const fifoArray = TsFifoArray(3);
fifoArray.push(2, 3, 4, 5);
console.log(fifoArray); // => [ 3, 4, 5 ]

#unshift()

const fifoArray = TsFifoArray(3, [ 0, 1, 2 ]);
fifoArray.unshift('a', 'b');
console.log(fifoArray); // => [ 'a', 'b', 0 ]

#splice()

const fifoArray = TsFifoArray(3, [ 0, 1, 2 ]);
fifoArray.splice(1, 2, 'a'); // at position 1, remove 2 elements and add 'a'
console.log(fifoArray); // => [ 0, 'a' ]

fifoArray.splice(1, 0, 'b'); // at posotion 1, remove 0 elements and add 'b'
console.log(fifoArray); // => [ 0, 'b', 'a' ]

.max

// if necessary, it chops the array down to the new max, removing elements from the end
const fifoArray = TsFifoArray(5, [ 0, 1, 2, 3, 4 ]);
console.log(fifoArray); // => [ 0, 1, 2, 3, 4 ]
fifoArray.max = 3;
console.log('new max:', fifoArray.max); // => new max: 3
console.log(fifoArray); // => [ 0, 1, 2 ]

fifoArray.max = 10;
fifoArray.push('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h');
console.log(fifoArray); // => [ 1, 2, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h' ]

Examples

See unit tests: test/index.test.ts

References

Here are several sources that helped me write this module:

• http://www.bennadel.com/blog/2308-creating-a-fixed-length-queue-in-javascript-using-arrays.htm
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty
• https://variadic.me/posts/2013-10-22-bind-call-and-apply-in-javascript.html