Append object parent key to children

I have the following object given:

{
  "groupA": [
    {data: 'foo'},
    {data: 'bar'}
  ],
  "groupB": [
    {data: 'hi'},
    {data: 'mom'}
  ]
}

I would like to append the parent object keys to all its array items like so:

{
  "groupA": [
    {data: 'foo', set: 'groupA'},
    {data: 'bar', set: 'groupA'}
  ],
  "groupB": [
    {data: 'hi', set: 'groupB'},
    {data: 'mom', set: 'groupB'}
  ]
}

How can I achieve this?

Answer

You can loop and set each item

const obj = {
  "groupA": [
    {data: 'foo'},
    {data: 'bar'}
  ],
  "groupB": [
    {data: 'hi'},
    {data: 'mom'}
  ]
};
Object.entries(obj).forEach(([key,val]) => val.forEach(item => item.set=key))
console.log(obj)