morsiesml / keymirror

Simple util to create an object with its keys mirrored as values. Standalone port of react/lib/keyMirror.

KeyMirror

Create an object with values equal to its key names.

I thought react/lib/keyMirror was useful and wanted to reuse it without any dependencies.

This is not my code, this is property of Facebook.

Why?

From this discussion:

The main purpose of keyMirror is to deal with the fact that Closure Compiler advanced mode crushes keys, which allows you to write code like

keyMirror({monkey: null, gorilla: null})

and have it become something like

k({m:null,g:null})

which evaluates to

{m:"m",g:"g"}

at runtime. If it was specified as a list of strings, they wouldn't get crushed matching the property names.

Usage

npm install keymirror

var keyMirror = require('keymirror');
var COLORS = keyMirror({blue: null, red: null});
var myColor = COLORS.blue;
var isColorValid = !!COLORS[myColor];

The last line could not be performed if the values of the generated enum were not equal to their keys.

Input: {key1: val1, key2: val2}

Output: {key1: key1, key2: key2}

I sometimes use this with lodash - use the following upon your first use of lodash to mix it in:

var _ = require('lodash');
_.mixin({keyMirror: require('keymirror')});
// Can now be used as _.keyMirror(object)