How to filter by region and remove it from the resulting array?

I have the following array structure:

const values = [{
    "region": "US", "content": "content 1", "value": "value1"
}, {
    "region": "US", "content": "content 2", "value": "value2"
}, {
    "region": "US", "content": "content 3", "value": "value3"
}, {
    "region": "LA", "content": "content 4", "value": "value4"
}, {
    "region": "LA", "content": "content 5", "value": "value5"
}, {
    "region": "LA", "content": "content 6", "value": "value6"
}, {
    "region": "LA", "content": "content 7", "value": "value7"
}]

and I am trying to transform it into the following – notice the region key is gone from the resulting object inside the output array:

const output = [{
    "US": [
        {"content": "content 1", "value": "value1"},
        {"content": "content 2", "value": "value2"},
        {"content": "content 3", "value": "value3"}
    ],
    "LA": [
        {"content": "content 4", "value": "value4"},
        {"content": "content 5", "value": "value5"},
        {"content": "content 6", "value": "value6"},
        {"content": "content 7", "value": "value7"}
    ]
}]

So far this is what I have tried:

let outputValues = [];

values.forEach(currentElement => {
    outputValues[currentElement.region].push(currentElement);
})

console.log(outputValues);

The above solution gives me the following error:

Uncaught TypeError: Cannot read properties of undefined (reading ‘push’)

Not sure why.

I have tried also:

# 1st option
outputValues[currentElement.region] = currentElement;

# 2nd option
outputValues[currentElement.region] = [];
outputValues[currentElement.region].push(currentElement);

But that adds only the last element from the main values array. What am I missing here?

>Solution :

If you do not want to keep the original objects, you could take the unwanted key as grouping value and delete this property while grouping.

const
    values = [{ region: "US", content: "content 1", value: "value1" }, { region: "US", content: "content 2", value: "value2" }, { region: "US", content: "content 3", value: "value3" }, { region: "LA", content: "content 4", value: "value4" }, { region: "LA", content: "content 5", value: "value5" }, { region: "LA", content: "content 6", value: "value6" }, { region: "LA", content: "content 7", value: "value7" }],
    result = Object.groupBy(values, o => {
        const group = o.region;
        delete o.region;
        return group;
    });

console.log(result);

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