exac

What is it?

exac = EXistential ACcessor - usefull feature from Groovy (read more http://docs.groovy-lang.org/latest/html/documentation/index.html#_safe_navigation_operator)

Why?

TL;DR; https://esdiscuss.org/topic/existential-operator-null-propagation-operator

We have config.json (NOTE: some fields are optional):

{
    ...
    "foo": {
      "bar": true,
      "baz": "foo",
      "aaa": {
        "bbb": "my_value",
        "ccc": false,
        "ddd": {
          "xxx": "brbrbr",
          "yyy": "mew-mew",
          "zzz": null
        },
        "eee": {
          "www": true,
          "ttt": [1, 2, 3]
        }
      }
    }
    ...
}

We want to do const v = config.aaa.ddd.zzz.kkk;

What should we do?

Option 1

if (config && config.aaa && config.aaa.ddd && config.aaa.ddd.zzz && config.aaa.ddd.zzz.kkk) {
    // bla-bla-bla
}

Option 2

const DEDAULT_VALUE = 'moo';
const v = config && config.aaa && config.aaa.ddd && config.aaa.ddd.zzz && config.aaa.ddd.zzz.kkk || DEFAUL_VALUE;

Option 3

const v = ((((config || {}).aaa || {}).ddd || {}).zzz || {}).kkk;

Have you ever seen the most pretty syntax?

Yep, sure! I show you (of course you have forgot CoffeeScript):

const v = config?.aaa?.ddd?.zzz?.kkk;

But it's not realized yet, it is only discussed... You can read more here: https://esdiscuss.org/topic/existential-operator-null-propagation-operator

OK, let's polyfill!

How to

const exac = require('exac'),
      config = exac(require('./config.json'));
      
//...

let v = config.aaa.ddd.zzz.kkk.$; // "$" at the end id mandatory - it's terminator

What is the $??? Yes, it's a little bit ugly, but it's only the way to terminate "test & get" recursion.

Installation

npm install exac --save --production

Pre-requisites

• Proxy (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy)
• ES Classes (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes)

Documentation

function exac(obj : Object, terminator = '$' : string) : Proxy

Params:

• obj - entity you want ot wrap
• terminator - symbol at the end of 'dot-notation' chain, by default $

Returns:

• <Proxy> - proxied object with lazy recursion

What's futher?

We're looking forward for a native implementation in ES or at least in Babel/Babylon

Todo

we need more tests!...

License

MIT