Is it possible to retrieve several columns using the pluck method in Underscore.js following the input from the where method, similar to LINQ

Question

Is it possible to retrieve several columns using the pluck method in Underscore.js following the input from the where method, similar to LINQ

var persons = [
    {name : "Alice", location : "paris", amount : 5},
    {name : "Bob", location : "tokyo", amount : 3},
    {name : "Eve", location : "london", amount : 10}
];

var filteredResults=_.pluck(_.where(persons, {location : "paris"}), 'name');

For instance: I am looking for name and amount.

javascript underscore.js

Answer 1

Answer №1

To project to multiple properties, utilize map instead of pluck:

var results = _.map(
    _.where(people, {city : "ny"}), 
    function(person) {
        return { firstName: person.firstName, qty: person.qty };
    }
);

[{"firstName":"Thein","qty":5},{"firstName":"Michael","qty":3}]

(Fiddle)

If desired, a helper method called "pluckMany" can be created to achieve the same functionality as pluck with variable arguments:

// first argument is the source array, followed by one or more property names
var pluckMany = function() {
    // get the property names to pluck
    var source = arguments[0];
    var propertiesToPluck = _.rest(arguments, 1);
    return _.map(source, function(item) {
        var obj = {};
        _.each(propertiesToPluck, function(property) {
            obj[property] = item[property]; 
        });
        return obj;
    });
};

The _.mixin function can be used to add a "pluckMany" function to the _ namespace. This allows for a simpler syntax like:

var results = _.chain(people).where({city : "ny"}).pluckMany( "firstName", "qty").value();

(Fiddle)

Answer 2

To project to multiple properties, utilize map instead of pluck:

var results = _.map(
    _.where(people, {city : "ny"}), 
    function(person) {
        return { firstName: person.firstName, qty: person.qty };
    }
);

[{"firstName":"Thein","qty":5},{"firstName":"Michael","qty":3}]

(Fiddle)

If desired, a helper method called "pluckMany" can be created to achieve the same functionality as pluck with variable arguments:

// first argument is the source array, followed by one or more property names
var pluckMany = function() {
    // get the property names to pluck
    var source = arguments[0];
    var propertiesToPluck = _.rest(arguments, 1);
    return _.map(source, function(item) {
        var obj = {};
        _.each(propertiesToPluck, function(property) {
            obj[property] = item[property]; 
        });
        return obj;
    });
};

The _.mixin function can be used to add a "pluckMany" function to the _ namespace. This allows for a simpler syntax like:

var results = _.chain(people).where({city : "ny"}).pluckMany( "firstName", "qty").value();

(Fiddle)

Answer 3

Answer №2

TL;DR Just use :

var results = _.chain(people)
    .where({ city: "ny" })
    .map(_.partialRight(_.pick, 'firstName', 'qty'))
    .value();

However, it's worth reading further for the explanations as the process of discovering this solution is more intriguing than the answer itself.

The basic structure would be (also applicable with lodash) :

_.map(array, function(obj) { return _.pick(obj, 'x', 'y', 'z'); });

Given this fundamental map function that transforms each element of a collection, there are various ways to customize it to your specific case (showcasing the versatility of map, essential in functional programming).

Below are several approaches to implement our solution :

var _ = require('lodash'); // @lodash 2.4.1 at the time of writing
// Use underscore if preferred, but refer to http://stackoverflow.com/questions/13789618/differences-between-lodash-and-underscore

/* Data */
var people = [{
    firstName: "Thein",
    city: "ny",
    qty: 5
}, {
    firstName: "Michael",
    city: "ny",
    qty: 3
}, {
    firstName: "Bloom",
    city: "nj",
    qty: 10
}];

...

console.log(results);

If you appreciate coding with underscore or lodash, exploring functional programming is highly recommended, since this style and many functions (map, reduce among others) originate from there.

Note: This seems to be a common query in the realm of underscore: https://github.com/jashkenas/underscore/issues/1104

It appears intentional that these functionalities are not included in underscore/lodash: "composability surpasses features". One could also say do one thing and do it well. Hence, the existence of _.mixin.

Answer 4

TL;DR Just use :

var results = _.chain(people)
    .where({ city: "ny" })
    .map(_.partialRight(_.pick, 'firstName', 'qty'))
    .value();

However, it's worth reading further for the explanations as the process of discovering this solution is more intriguing than the answer itself.

The basic structure would be (also applicable with lodash) :

_.map(array, function(obj) { return _.pick(obj, 'x', 'y', 'z'); });

Given this fundamental map function that transforms each element of a collection, there are various ways to customize it to your specific case (showcasing the versatility of map, essential in functional programming).

Below are several approaches to implement our solution :

var _ = require('lodash'); // @lodash 2.4.1 at the time of writing
// Use underscore if preferred, but refer to http://stackoverflow.com/questions/13789618/differences-between-lodash-and-underscore

/* Data */
var people = [{
    firstName: "Thein",
    city: "ny",
    qty: 5
}, {
    firstName: "Michael",
    city: "ny",
    qty: 3
}, {
    firstName: "Bloom",
    city: "nj",
    qty: 10
}];

...

console.log(results);

If you appreciate coding with underscore or lodash, exploring functional programming is highly recommended, since this style and many functions (map, reduce among others) originate from there.

Note: This seems to be a common query in the realm of underscore: https://github.com/jashkenas/underscore/issues/1104

It appears intentional that these functionalities are not included in underscore/lodash: "composability surpasses features". One could also say do one thing and do it well. Hence, the existence of _.mixin.

Answer 5

Answer №3

Ah, how I long for the day when pluck will accept an array as input. But for now, you can achieve a similar result with this workaround:

const pluckFields = (arr, fields) => _.map(arr, item => _.pick(item, fields))

Answer 6

Ah, how I long for the day when pluck will accept an array as input. But for now, you can achieve a similar result with this workaround:

const pluckFields = (arr, fields) => _.map(arr, item => _.pick(item, fields))

Answer 7

Answer №4

From what I've gathered, the individual who posed the question is interested in simplifying an array of objects by extracting only a few key properties from each object.

There are countless methods to achieve this outcome using various tools, but the one that resonates with me is as follows. Start by initializing an empty result object, which will serve as the context within the function. Then, utilize a combination of iteration using _.each and property selection with _.pick to extract the desired fields:

var myObjects = [
    { "first" : "Alice",
      "last" : "Smith",
      "age" : 30
    },
    { "first" : "Bob",
      "last" : "Johnson",
      "age" : 45
    }
];

var result = [];
_.each( myObjects, function(item) { this.push(_.pick(item,"first","age")) }, result );

console.log(result);

Answer 8

From what I've gathered, the individual who posed the question is interested in simplifying an array of objects by extracting only a few key properties from each object.

There are countless methods to achieve this outcome using various tools, but the one that resonates with me is as follows. Start by initializing an empty result object, which will serve as the context within the function. Then, utilize a combination of iteration using _.each and property selection with _.pick to extract the desired fields:

var myObjects = [
    { "first" : "Alice",
      "last" : "Smith",
      "age" : 30
    },
    { "first" : "Bob",
      "last" : "Johnson",
      "age" : 45
    }
];

var result = [];
_.each( myObjects, function(item) { this.push(_.pick(item,"first","age")) }, result );

console.log(result);

Answer 9

Answer №5

YAAUu-Yet Another Response Employing underscore...

// ensure to utilize a capable browser for executing this code snippet, ideally an es6-compliant browser
let individuals = [{
    firstName: "Alice",
    city: "la",
    qty: 7
  },
  {
    firstName: "Sam",
    city: "la",
    qty: 2
  },
  {
    firstName: "Mia",
    city: "sf",
    qty: 6
  }
];
// you have the option to select the properties you desire 
let selecting = _.iteratee((person) => _(person).pick("firstName", "city"));
// alternatively, you can exclude the properties you don't need
let excluding = _.iteratee((person) => _(person).omit("qty"));
// establish the filter based on city
let residing = (individuals, city) => _(individuals).where({
  "city": city
});
// incorporate the "filter by city" into a mixin (presuming it will be reused multiple times)
_.mixin({
  residing: residing
});
// perform the operation (twice), 
// these chain methods could also be integrated into a mixin
console.log("outcomes with selected properties:", _(individuals).chain().residing("la").map(selecting).value());
console.log("results with excluded properties:", _(individuals).chain().residing("la").map(excluding).value());

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

Answer 10

YAAUu-Yet Another Response Employing underscore...

// ensure to utilize a capable browser for executing this code snippet, ideally an es6-compliant browser
let individuals = [{
    firstName: "Alice",
    city: "la",
    qty: 7
  },
  {
    firstName: "Sam",
    city: "la",
    qty: 2
  },
  {
    firstName: "Mia",
    city: "sf",
    qty: 6
  }
];
// you have the option to select the properties you desire 
let selecting = _.iteratee((person) => _(person).pick("firstName", "city"));
// alternatively, you can exclude the properties you don't need
let excluding = _.iteratee((person) => _(person).omit("qty"));
// establish the filter based on city
let residing = (individuals, city) => _(individuals).where({
  "city": city
});
// incorporate the "filter by city" into a mixin (presuming it will be reused multiple times)
_.mixin({
  residing: residing
});
// perform the operation (twice), 
// these chain methods could also be integrated into a mixin
console.log("outcomes with selected properties:", _(individuals).chain().residing("la").map(selecting).value());
console.log("results with excluded properties:", _(individuals).chain().residing("la").map(excluding).value());

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>

Answer 11

Answer №6

A more concise approach could be to use a single line of code:

let selected = _.pick(_.where(people, {city: "ny"}), 'firstName', 'qty');

Answer 12

A more concise approach could be to use a single line of code:

let selected = _.pick(_.where(people, {city: "ny"}), 'firstName', 'qty');

Answer 13

Answer №7

Avoid using pluck, you can achieve the desired result with omit too.

const updatedList = _.map(users, function(user) {
  return _.omit(user, 'email');
});

Answer 14

Avoid using pluck, you can achieve the desired result with omit too.

const updatedList = _.map(users, function(user) {
  return _.omit(user, 'email');
});

Is it possible to retrieve several columns using the pluck method in Underscore.js following the input from the where method, similar to LINQ

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Similar questions

The input 'Element' does not match the expected parameter 'ReactElement<any>' in this context

Getting rid of an Ajax loader graphic after a period of time

Is there a way to work around the CORS policy in order to fetch data from URLs?

By default, the HTML table will highlight the specific column based on the current month using either AngularJS or JavaScript upon loading

Is it possible that adding html tables together could result in the numbers being concatenated instead of summed?

Converting a TypeScript object into a JSON string

Toggling forms with HTML <select> elements: A step-by-step guide

Increasing the sms counter in javascript once it reaches 160 characters

What do you mean my cookie isn't working?

What is the best way to incorporate Drift bot JS code into a static React NextJs application, such as a landing page?

Why won't the jQuery function trigger when I click, but only responds when I move the cursor?

When I use my loop to generate Google Map markers, the positioning is not accurate and the markers do not appear on the map. However, manually inputting the positions

The <br/> tag is not functioning properly when retrieving text from a MySQL query

Iteratively traverse the object to establish connections between parent and child elements

Viewer model aggregation - coordinating problem

Different ways to categorize and tally a collection of objects

An exploration on integrating a controller into an Angular directive class using Typescript

Leveraging Vue.js to preload data with client-side rendering

Having trouble getting the CSS class to work in MVC4 with jQuery implementation

`Only firing event listener once`