Invoke getter/setter functions on array-like objects
This little module provides an
ArrayIndex constructor function that you can
inherit from with your own objects. When a numbered property gets read, then the
ArrayIndex.get function on the object will be invoked. When a numbered property gets
set, then the
ArrayIndex.set function on the object will be invoked.
$ npm install array-index
A quick silly example, using
Math.sqrt() for the "getter":
var ArrayIndex = require'array-index';// let's just create a singleton instance.var a = ;// the "ArrayIndex.get" function is invoked for each "a[n]" access.// it is given a single argument, the "index" currently being accessed.// so here, we're passing in the `Math.sqrt()` function, so accessing// "a" will return `Math.sqrt(9)`.aArrayIndexget = Mathsqrt;// the "ArrayIndex.get" and "ArrayIndex.set" functions are only invoked up// to "a.length", so we must set that manually.alength = 10;console.loga;// [ 0,// 1,// 1.4142135623730951,// 1.7320508075688772,// 2,// 2.23606797749979,// 2.449489742783178,// 2.6457513110645907,// 2.8284271247461903,// 3 ]
Here's an example of creating a subclass of
var ArrayIndex = require'array-index';var inherits = require'util'inherits;// be sure to call the ArrayIndex constructor in your own constructorArrayIndexcallthis length;// the "set" object will contain values at indexes previously set,// so that they can be returned in the "getter" function. This is just a// silly example, your subclass will have more meaningful logic.ObjectdefinePropertythis 'set'value: Objectcreatenullenumerable: false;// inherit from the ArrayIndex's prototypeinheritsMyArray ArrayIndex;MyArrayprototypeArrayIndexget =if index in thisset return thissetindex;return index * 2;;MyArrayprototypeArrayIndexset =thissetindex = v;;// and now you can create some instancesvar a = 15;a9 = a10 = a14 = '_';a0 = 'nate';console.loga;// [ 'nate', 2, 4, 6, 8, 10, 12, 14, 16, '_', '_', 22, 24, 26, '_' ]
ArrayIndex base class is meant to be subclassed, but it also has a few
convenient functions built-in.
The length of the ArrayIndex instance. The
ArrayIndex.set functions will
only be invoked on the object up to this "length". You may set this length at any
time to adjust the amount range where the getters/setters will be invoked.
Returns a new regular Array instance with the same values that this ArrayIndex
class would have. This function calls the
ArrayIndex.get function repeatedly from
0...length-1 and returns the "flattened" array instance.
ArrayIndex instances get basic support for
JSON.stringify(), which is
the same as a "flattened" Array being stringified.
toString() override is basically just
inspect() implementation for the REPL attempts to mimic what a regular
Array looks like in the REPL.
(The MIT License)
Copyright (c) 2012 Nathan Rajlich <firstname.lastname@example.org>
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.