Safe-obj

Underscore helpers to make object accessors safe

I came (partly) from a Perl background where you could say $obj->{thing}->{another_thing}->{more_things}, and it would not blow up even if $obj was totally empty. Similarly, you could say $obj->{thing}->{foo} = 'bar', even if $obj had no property called 'thing'. I don't miss everything about Perl, but I do miss that. In javascript, you'd have to say:

if (obj && obj.thing && obj.thing.another_thing && obj.thing.another_thing.more_things) {
  // I want to die a little bit
}

So this module is basically auto-vivification for javascript.

Install

npm install safe-obj --save

Usage

Server

As of v1.0.0, this module works with both lodash and underscore, though it requires using _.safe(obj, path) with lodash since _(obj).safe(path) triggers lodash's chaining.

safe-obj exports an object that can be mixed into underscore/lodash like this:

_.mixin(require('safe-obj'));

that let's you access object properties with wild abandon.

Client

Additionally, as of v1.0.0, it works on the client side. If window._ is defined (i.e. lodash or underscore has been loaded), _.safe will add an _safe property to it, which you can mix in with _.mixin(_._safe).

On the client, just include the script after underscore or lodash:

<script src="/underscore.js"></script>
<script src="path/to/safe-obj/dist/safe.js"></script>

and then mix it in:

<script>
  (function() {
    _.mixin(_._safe);
  })();
</script>

API

Safe

Let's you access object properties (and array indices too!) regardless of whether they exist. If, at any point, a property returns undefined (where calling another object accessor would blow up), safe immediately just returns undefined (or a default, if you provide one).

var obj = {}

// returns undefined
var innerProp = _(obj).safe('foo.bar.baz.0.hello.world'); 

// returns [] - useful if you want to call array methods but don't want to check the type
var anotherProp = _(obj).safe('a.brave.new.world', []); 

Expand

Let's you assign to any arbitrarily deep and non-existent property on an object. Any non-existent properties are expanded into objects.

var obj = {}

_(obj).expand('foo.bar.baz', 'hello world');

// obj now equals: {
//   foo: {
//     bar: {
//       baz: 'hello world'
//     }
//   }
// }

Expand is likely to be finnicky (at the moment) with expanding arrays. It's untested, and my guess is that it will create object properties with numbers. Something like

property: {
  0: {
    // more stuff
  }
}

I'd like to make that work more as expected in a future release, but for now, don't expect it to work.

Ensure

Sets a path to a given value unless that path already has a value. Also allows an optional list of "disallowed" values.

var obj = {
  foo: {
    bar: 'baz'
  }
};

// This will have no effect on obj since 'foo.bar' already has a value
_(obj).ensure('foo.bar', 'a default value');

obj = {
  foo: {}
};

// This will set obj.foo equal to { bar: 'a default value' }
_(obj).ensure('foo.bar', 'a default value');

obj = {
  foo: {
    bar: 'nope'
  }
};

// This says don't allow 'nope' as a value of foo.bar, thus it will use the default
_(obj).ensure('foo.bar', [ 'nope' ], 'a default value');

AllOf

Uses safe to return true if all the paths exist in the object or false if any is missing.

var obj = {
  foo: {
    bar: 'baz'
  }
};

_(obj).allOf('foo.bar', 'hello.world'); // returns false

// or
// _(obj).allOf(['foo.bar', 'hello.world']);

AnyOf

Like allOf but returns true if any of the paths exist.

var obj = {
  foo: {
    bar: 'baz'
  }
};

_(obj).anyOf('foo.bar', 'hello.world'); // returns true

NoneOf

Like allOf and anyOf but only returns true when none of the paths exist.

var obj = {
  foo: {
    bar: 'baz'
  }
};

_(obj).noneOf('foo.bar', 'hello.world'); // returns false