How to chain get and map the result with lodash? - lodash

Question

I've got a list I'm trying to pull an object from using _.get but following that selection I need to loop over the object to create a new property. So far I've been successful using a combination of _.get and _.map as shown below but I'm hoping I can use _.chain in some way.
var selected = _.get(results, selectedId);
return _.map([selected], result => {
var reviews = result.reviews.map(review => {
var reviewed = review.userId === authenticatedUserId;
return _.extend({}, review, {reviewed: reviewed});
});
return _.extend({}, result, {reviews: reviews});
})[0];
Is it possible to do a transform like this using something other than map (as map required me to break this up/ creating an array with a solo item inside it). Thank you in advance!

Answer 1

I can see that you're creating unnecessary map() calls, you can simply reduce all those work into something like this:
var output = {
reviews: _.map(results[selectedId], function(review) {
return _.defaults({
reviewed: review.userId === authenticatedUserId
}, review);
})
};
The defaults() method is similar to extend() except once a property is set, additional values of the same property are ignored.
var selectedId = 1;
var authenticatedUserId = 1;
var results = {
1: [
{ userId: 1, text: 'hello' },
{ userId: 2, text: 'hey' },
{ userId: 1, text: 'world?' },
{ userId: 2, text: 'nah' },
]
};
var output = {
reviews: _.map(results[selectedId], function(review) {
return _.defaults({
reviewed: review.userId === authenticatedUserId
}, review);
})
};
document.body.innerHTML = '<pre>' + JSON.stringify(output, 0, 4) + '</pre>';
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>