CODEWITHSUNDEEP
javascriptarraysunderscore.js
ms87
ms87

Reputation: 17492

Underscore equivalent of _.pick for arrays

I understand that pick is used to get back an object with only specified properties:

_.pick({name: 'moe', age: 50, userid: 'moe1'}, 'name', 'age');
=> {name: 'moe', age: 50}

How would I perform that same operation on an array, say I have an array such as:

[{name: 'moe1', age: 50, userid: 'moe1'},
{name: 'moe2', age: 50, userid: 'moe1'},
{name: 'moe3', age: 50, userid: 'moe1'}]

and I want to map it to an array so to include only the name and age properties, like:

[{name: 'moe1', age: 50},
{name: 'moe2', age: 50},
{name: 'moe3', age: 50}]

Do I have to do an each() on the array then perform a pick() on each object, or is there a cleaner way?

EDIT

Sorry but just another small requirement, how would I perform a where (i.e. get all those whose age is greater than 50) and then perform the pick? EDIT got it done like this, was unaware of how chaining works in underscore.

_(data).reject(function (r) { return d.age<51; }).map(function (o) {
            return _.pick(o, "age", "name");
});

Upvotes: 18

Views: 20599

Answers (2)

Almas Kamitov
Almas Kamitov

Reputation: 103

You can take just one lodash method for that (~50kb import):

npm i lodash.pick

Solution:

const pick = require('lodash.pick')

const filterValues = ['name', 'age']
const arr = [
    { name: 'moe1', age: 52, userid: 'moe1' },
    { name: 'moe2', age: 50, userid: 'moe1' },
    { name: 'moe3', age: 50, userid: 'moe1' }
]

const result = arr
    .filter(item => item.age < 51)
    .map(item => pick(item, filterValues))

Output:

[ { name: 'moe2', age: 50 }, { name: 'moe3', age: 50 } ]

Upvotes: 1

thefourtheye
thefourtheye

Reputation: 239473

You have to use _.map and apply the same _.pick on all the objects.

var data = [{name: 'moe1', age: 30, userid: 'moe1'},
            {name: 'moe2', age: 50, userid: 'moe1'},
            {name: 'moe3', age: 60, userid: 'moe1'}];

var result = _.map(data, function(currentObject) {
    return _.pick(currentObject, "name", "age");
});

console.log(result);

Output

[ { name: 'moe1', age: 50 },
  { name: 'moe2', age: 50 },
  { name: 'moe3', age: 50 } ]

If you want to get the objects in which the age is > 50, you might want to do, like this

var data = [{name: 'moe1', age: 30, userid: 'moe1'},
            {name: 'moe2', age: 50, userid: 'moe1'},
            {name: 'moe3', age: 60, userid: 'moe1'}];

function filterByAge(currentObject) {
    return currentObject.age && currentObject.age > 50;
}

function omitUserId(currentObject) {
    return _.omit(currentObject, "userid");
}

var result = _.map(_.filter(data, filterByAge), omitUserId);    
console.log(result);

Output

[ { name: 'moe3', age: 60 } ]

You can do the same with chaining, as suggested by rightfold, like this

var result = _.chain(data).filter(filterByAge).map(omitUserId).value();

Upvotes: 34

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