Find properties of JS object with truthy values using lodash

var foo = {
    alpha: true,
    beta: false,
    gamma: true
};

var t1 = _.keys(_.pick(foo, _.identity));
console.log(t1);

var t2 = _(foo).pick(_.identity).keys().value();
console.log(t2);
<script type="text/javascript" src="//cdnjs.cloudflare.com/ajax/libs/lodash.js/3.5.0/lodash.min.js"></script>
<script src="https://getfirebug.com/firebug-lite-debug.js"></script>

Edit:
As noted by @backdesk, _.pick no longer works for lodash 4 because _.pickBy was split out.

var foo = {
    alpha: true,
    beta: false,
    gamma: true
};

var t1 = _.keys(_.pickBy(foo, _.identity));
console.log(t1);

var t2 = _(foo).pickBy(_.identity).keys().value();
console.log(t2);

// _.pickBy defaults to _.identity

var t3 = _.keys(_.pickBy(foo));
console.log(t3);

var t4 = _(foo).pickBy().keys().value();
console.log(t4);
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.8.2/lodash.min.js"></script>
<script src="https://getfirebug.com/firebug-lite-debug.js"></script>


I found an answer which simultaneously feels kludgy and elegant.

var foo = {
    alpha: true,
    beta: false,
    gamma: true
};
_.invert(foo, true).true

// yields -> ["alpha", "gamma"]

pickBy in loDash by default uses _.identity to filter properties so you can use it like this:

_.pickBy({'a': undefined, 'b':1, c:{}});

// => Object {b: 1, c: Object}

Tags:

Javascript

Lodash

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