javascript - The index of an item in OrderedMap - Stack Overflow

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As the title states, I want to get the index of a particular item. Is there a way to do this?

const key = 1
const map = new Immutable.OrderedMap([5, 'a'], [3, 'b'], [1, 'c'])

So, in this case, the index of key would be 2.

As the title states, I want to get the index of a particular item. Is there a way to do this?

const key = 1
const map = new Immutable.OrderedMap([5, 'a'], [3, 'b'], [1, 'c'])

So, in this case, the index of key would be 2.

• javascript
• immutable.js

Share Improve this question Follow edited Sep 10, 2015 at 20:33 Felix Kling 817k181181 gold badges1.1k1.1k silver badges1.2k1.2k bronze badges asked Sep 10, 2015 at 20:27 Azad SalahliAzad Salahli 91633 gold badges1515 silver badges3131 bronze badges

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3 Answers 3

Sorted by: Reset to default 6

You can get the key sequence from the map:

let index = map.keySeq().findIndex(k => k === key);

See the docs for more info.

Alternatively, you could explicitly iterate over the keys and pare them:

function findIndexOfKey(map, key) {
    let index = -1;
    for (let k of map.keys()) {
        index += 1;
        if (k === key) {
            break
        }
    }
    return index;
}

the best way to do it would be the way immutablejs inners does it.

Like this:

const index = orderedMap._map.get(k);

https://github./facebook/immutable-js/blob/master/src/OrderedMap.js#L43

If you need the key and value as well as the index, you can iterate over the entrySeq

orderedMap.entrySeq().forEach((tuple,i) => console.log(`Index ${i} \n Key ${tuple[0]} \n Value ${tuple[1]}`)

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