How to retrieve the key from an array of values of a JSON object?

Question

Let there is an object which has values as arrays. For example,

    const obj = {
      'abc': ['xyz','tuv'],
      'def': ['qrs']
    }

How can we get the key of 'tuv' from the object?

This is different from this question, where the value was not an array. How to get a key in a JavaScript object by its value?

Are you looking for a result of 'abc' given the value 'tuv'? — Grax32
– Grax32, Commented Jan 17, 2020 at 11:47
Does this answer your question? How to get a key in a JavaScript object by its value? — VLAZ
– VLAZ, Commented Jan 17, 2020 at 11:51
Not an exact dupe, since it's doing an exact match of the value to get the key but the only change needed is to add array lookup instead of exact matching. And array lookup is a trivial task that is a solved problem. — VLAZ
– VLAZ, Commented Jan 17, 2020 at 11:52

Nina Scholz · Accepted Answer · 2020-01-17 11:47:30Z

3

You could get the keys and filter by checking the values.

const
    getKeys = (object, value) => Object.keys(object).filter(k => object[k].includes(value)),
    obj = { abc: ['xyz','tuv'], def: ['qrs'] };
    
console.log(getKeys(obj, 'tuv'));

answered Jan 17, 2020 at 11:47

Nina Scholz

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Comments

Reza · Accepted Answer · 2020-01-17 11:44:36Z

1

I am assuming one value will not have multiple keys.

const getKeyByValue = (object, value) => Object.keys(object)
  .map(key => object[key].map(val => { if (val === value) { return key }}))
  .flat().filter(key => key)[0] || false

So, if we want to get the key of 'tuv', we can call this method like this,

getKeyByValue(obj, 'tuv')

answered Jan 17, 2020 at 11:44

Reza

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2 Comments

evolutionxbox Over a year ago

object[key].map(val => { if (val === value) { return key }}) should probably be filter?

Reza Over a year ago

Yeah, that would be another way of doing it.

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