selectn
Resolves deeply-nested object properties via dot or bracket-notation for Node.js and the browser.
So you can do:
selectn('info.name.full', person)
instead of:
person && person.info && person.info.name && person.info.name.full
Features
- Avoids
if (obj && obj.a && obj.a.b && obj.a.b.c) { return obj.a.b.c; }
. - Supports multiple levels of array nesting (i.e.
group[0].section.a.seat[3]
). - Supports dashed key access (i.e.
stats.temperature-today
). - Partial application supported.
- Functions generated by
selectn
can be passed to applicative functors like Array.prototype.map and Array.prototype.filter. - Works where typeof fails (i.e. deeply nested properties).
- ES5 and non-ES5 compatible.
- CommonJS, AMD, and legacy-global compatible.
- Provides access to global object if no object reference is given.
Non-Features
Installation
component
$ component install wilmoore/selectn
bower
$ bower install selectn
npm
jam
$ jam install selectn
volo
$ volo add wilmoore/selectn
global
<script src="https://raw.github.com/wilmoore/selectn/master/selectn.min.js"></script>
Examples
Nested property access
Given the following object:
var talk = {
info: { name: 'Go Ahead, Make a Mess' }
};
Apply the selectn
function to the path
and object
parameters for error-free access to deeply nested properties.
selectn('info.name', talk);
// => 'Go Ahead, Make a Mess'
Dashed keys
Given the following object:
var talk = {
info: { 'attendee-count': 200 }
};
Apply the selectn
function to the path
and object
parameters for error-free access to deeply nested properties.
selectn('info.attendee-count', talk);
// => 200
Iterator
Given the following list:
var talks = [
{ info: { name: 'Go Ahead, Make a Mess' }},
{ info: { name: 'Silex Anatomy' }},
{ info: { name: 'Unit Testing in Python' }},
{ info: { name: 'Setting the Stage' }}
];
The generated function can be used as a predicate for map:
var query = selectn('info.name');
//=> [Function]
talks.map(query);
// => [ 'Go Ahead, Make a Mess', 'Silex Anatomy', 'Unit Testing in Python', 'Setting the Stage' ]
Predicate
Given the following object of language strings:
var language = [
{ strings: { en: { name: 'english' } }},
{ strings: { es: { name: 'spanish' } }},
{ strings: { km: { name: 'khmer' } }},
{ strings: { es: { name: 'spanish' } }},
];
The generated function can be used as a predicate for filter:
var spanish = selectn('strings.es');
//=> [Function]
language.filter(spanish).length;
//=> 2
Callback
You expect the following JSON data from an XMLHttpRequest:
var data = { Client: { Message: { id: d50afb80-a6be-11e2-9e96-0800200c9a66 } } };
Access the Client.Message.id
property and log the result to the console (using promises):
$.ajax({...})
.then(selectn('Client.Message.id'))
.then(console.log.bind(console));
//=> d50afb80-a6be-11e2-9e96-0800200c9a66
NOTE: Even if you don't use this methodology in production code, it can be a handy timesaver in terms of quick debugging.
Rationale
In larger, data-driven applications, there tends to be a need to do a lot of deep object access which can quickly lead to code like this:
var name;
if (contact && contact.info && contact.info.name) {
name = contact.info.name.full || 'unknown';
}
The following is much more concise:
var name = selectn('info.name.full')(contact) || 'unknown';
Neckbeard Info
In case you care about this sort of thing, we are able to do normal function application as well as partially apply when that is convenient due to currying
.
selectn('info.name.full', contact)
(normal function application)selectn('info.name.full')(contact)
(partial application without a partial
helper like Function.prototype.bind
)
Since selectn
is a 2-ary function, we don't need to use an external library for currying as the algorithm is simple.
Alternatives
- You can use typeof; however, typeof only "appears" to work due to the way the global scope is implied.
- Other solutions involve eval and/or Function (
eval
in disguise).
Inspiration
License
MIT