Lodash : return first key of object whose value(i.e Array) has a given element (i.e string) in it

Question

I have an object like:

var obj = {
  "01": ["a","b"],
  "03": ["c","d"],
  "04": ["e","c"]
};

and I know an array element ( say "c") of the object key's value then How to find first key value i.e "03" using lodash without using if else?

I tried like this using lodash and if else:

var rId = "";
_.forOwn(obj, function (array, id) {
     if (_.indexOf(array, "c") >= 0) {
           rId = id;
           return false;
     }
});

console.log(rId); // "03"

Expected Result: first key i.e "03" if element matches else "".

After seeing comments: Now I'm also curious to know about

Does I need to go with native javascript(hard to read program in the cases if we use more than 2 if blocks) or lodash way(easily readable program solution in one line)?

please add the wanted result.

Nina Scholz
– Nina Scholz

2016-04-30 19:24:10 +00:00
Commented Apr 30, 2016 at 19:24 — Nina Scholz
– Nina Scholz, Commented Apr 30, 2016 at 19:24
how about native javascript solution?

RomanPerekhrest
– RomanPerekhrest

2016-04-30 19:25:14 +00:00
Commented Apr 30, 2016 at 19:25 — RomanPerekhrest
– RomanPerekhrest, Commented Apr 30, 2016 at 19:25
Without lodash: jsfiddle.net/rayon_1990/5pd8sq5g

Rayon
– Rayon

2016-04-30 19:27:14 +00:00
Commented Apr 30, 2016 at 19:27 — Rayon
– Rayon, Commented Apr 30, 2016 at 19:27

Akshat Mahajan · Accepted Answer · 2016-04-30 20:55:11Z

49

Since you just want a way to be able to find a key using a simple Lodash command, the following should work:

_.findKey(obj, function(item) { return item.indexOf("c") !== -1; });

or, using ES6 syntax,

_.findKey(obj, (item) => (item.indexOf("c") !== -1));

This returns "03" for your example.

The predicate function - the second argument to findKey() - has automatic access to the value of the key. If nothing is found matching the predicate function, undefined is returned.

Documentation for findKey() is here.

Examples taken from the documentation:

var users = {
  'barney':  { 'age': 36, 'active': true },
  'fred':    { 'age': 40, 'active': false },
  'pebbles': { 'age': 1,  'active': true }
};

_.findKey(users, function(o) { return o.age < 40; });
// → 'barney' (iteration order is not guaranteed)

// The `_.matches` iteratee shorthand.
_.findKey(users, { 'age': 1, 'active': true });
// → 'pebbles'

// The `_.matchesProperty` iteratee shorthand.
_.findKey(users, ['active', false]);
// → 'fred'

// The `_.property` iteratee shorthand.
_.findKey(users, 'active');
// → 'barney'

edited Apr 30, 2016 at 20:55

answered Apr 30, 2016 at 19:31

Akshat Mahajan

9,8764 gold badges38 silver badges46 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Sandeep Sharma Over a year ago

I'm doing node.js programming. Now I'm also curious to know about Does I need to go with native javascript(hard to read program) or lodash way(easily readable program)?

Akshat Mahajan Over a year ago

@SandeepSharma Use what you feel is best for your needs and requirements. If you already have Lodash, I think it's worth sticking with it. Lodash's API is what Javascript's semantics should have been. Since it's server-side, there are no real arguments against using Lodash - on the client, it's a bulky library, but who cares about library size on the server? No one. There is a tiny performance hit, but not enough to really make a difference.

Akshat Mahajan Over a year ago

@SandeepSharma Also, Javascript programs don't have to be hard to read. If your Javascript is hard to read, it's because you're making it needlessly complicated. JS can be as simple and clean to read as Lodash if you take the time to subscribe to proper patterns. Lodash is Javascript, after all.

Akshat Mahajan Over a year ago

@SandeepSharma Anyway, if this answer correctly answers your original question, you should mark it as accepted answer.

Sandeep Sharma Over a year ago

you have fixed the item[0] to zeroth index.

Роман Парадеев · Accepted Answer · 2016-04-30 21:45:03Z

11

The irony is it is not any harder to implement without any libs.

Object.keys(obj).filter(x => obj[x].includes("c"))[0]

answered Apr 30, 2016 at 21:45

Роман Парадеев

4,28621 silver badges37 bronze badges

2 Comments

ContinuousLoad Over a year ago

Good point! You could even use .find(...) instead of .filter(...)[0]: Object.keys(obj).find(x => obj[x].includes("c"))

Sunny Patel Over a year ago

Keep in mind this iterates over all the keys and doesn't short-circuit like other solutions.

Redu · Accepted Answer · 2016-04-30 22:39:09Z

1

Here comes a single liner answer from the future. Currently only works in Firefox 47 on. Part of ES7 proposal.

var obj = {
  "01": ["a","b"],
  "03": ["c","d"],
  "04": ["e","c"]
},
    res = Object.entries(obj).find(e => e[1].includes("c"))[0];
document.write(res);

edited Apr 30, 2016 at 22:39

answered Apr 30, 2016 at 19:48

Redu

26.3k6 gold badges61 silver badges84 bronze badges

3 Comments

Роман Парадеев Over a year ago

I believe is not on a part of ES7 but rather ES8.

Роман Парадеев Over a year ago

You probably shoud update find condition, since now you are not searching through the whole array, but only the first item.

Redu Over a year ago

@Роман Парадеев Yes you are right i have misunderstood the quotestion. I will correct accordingly. By the way your solution is perfect and deserves a +.

RomanPerekhrest · Accepted Answer · 2016-04-30 19:55:40Z

0

As an alternative solution: consider native Javascript approach using Object.keys and Array.some functions:

var obj = {"01": ["a","b"],"03": ["c","d"],"04": ["e","c"]},
        search_str = "c", key = "";

Object.keys(obj).some(function(k) { return obj[k].indexOf(search_str) !== -1 && (key = k); });
// the same with ES6 syntax:
// Object.keys(obj).some((k) => obj[k].indexOf(search_str) !== -1 && (key = k));

console.log(key);  // "03"

edited Apr 30, 2016 at 19:55

answered Apr 30, 2016 at 19:33

RomanPerekhrest

93.1k4 gold badges75 silver badges112 bronze badges

Collectives™ on Stack Overflow

Lodash : return first key of object whose value(i.e Array) has a given element (i.e string) in it

4 Answers 4

5 Comments

2 Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

5 Comments

2 Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related