array-index
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
__get__
function on the object will be invoked. When a numbered property gets
set, then the __set__
function on the object will be invoked.
Installation
Install with npm
:
$ npm install array-index
Examples
A quick silly example, using Math.sqrt()
for the "getter":
var ArrayIndex = require('array-index')
var a = new ArrayIndex()
a.__get__ = Math.sqrt
a.length = 10
console.log(a)
Here's an example of creating a subclass of ArrayIndex
using util.inherits()
:
var ArrayIndex = require('array-index')
var inherits = require('util').inherits
function MyArray (length) {
ArrayIndex.call(this, length)
Object.defineProperty(this, 'set', {
value: Object.create(null),
enumerable: false
})
}
inherits(MyArray, ArrayIndex)
MyArray.prototype.__get__ = function (index) {
if (index in this.set) return this.set[index]
return index * 2
}
MyArray.prototype.__set__ = function (index, v) {
this.set[index] = v
}
var a = new MyArray(15)
a[9] = a[10] = a[14] = '_'
a[0] = 'nate'
console.log(a)
API
The ArrayIndex
base class is meant to be subclassed, but it also has a few
convenient functions built-in.
"length" -> Number
The length of the ArrayIndex instance. The __get__
and __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.
"toArray()" -> Array
Returns a new regular Array instance with the same values that this ArrayIndex
class would have. This function calls the __get__
function repeatedly from
0...length-1
and returns the "flattened" array instance.
"toJSON()" -> Array
All ArrayIndex
instances get basic support for JSON.stringify()
, which is
the same as a "flattened" Array being stringified.
"toString()" -> String
The toString()
override is basically just array.toArray().toString()
.
"format()" -> String
The inspect()
implementation for the REPL attempts to mimic what a regular
Array looks like in the REPL.
License
(The MIT License)
Copyright (c) 2012 Nathan Rajlich <nathan@tootallnate.net>
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.