Invert object keys with value array

Question

I am working on a programming challenge. I need to invert this object:

{
   apple: [40, 49],
   orange: [20, 21],
   pear: [2, 50, 19]
}

to come out as

{
   40: "apple",
   49: "apple",
   20: "orange",
   21: "orange",
   2: "pear",
   50: "pear",
   19: "pear",
}

This is pretty easy to do with a for-loop, but one of the rules to the challenge is no for-loops or additional libraries.

Here's my solution using for-loops, is it possible to do it without the use of a for-loop:

var temp = {}
for (var key in fruit) {
    for (var i in fruit[key]) {
        temp[fruit[key][i]] = key;
    }
}
console.log(temp);

mickl · Accepted Answer · 2020-03-24 23:25:36Z

1

You can try using array.reduce and Object.entries:

let input = {
   apple: [40, 49],
   orange: [20, 21],
   pear: [2, 50, 19]
};

let result = Object.entries(input).reduce((acc, current) => {
    let [k,v] = current;
    v.forEach(val => acc[val] = k);
    return acc;
}, {})

console.log(result);

answered Mar 24, 2020 at 23:25

mickl

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Comments

Jonas Wilms · Accepted Answer · 2020-03-24 23:27:02Z

1

  const temp = Object.fromEntries(Object.entries(fruit).flatMap(([k, vs]) => vs.map(v => [v, k])));

This is basically with loops too, just way more obscure.

answered Mar 24, 2020 at 23:27

Jonas Wilms

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1 Comment

Jaromanda X Over a year ago

with loops - but not a for loop - so it's fine

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