Javascript multiple value object to simple array

Question

I have an object like this:

obj1 = {A: {bottom: 63, mid: 4, top: 15}, B: {bottom: 30, mid: 23, top: 5}, C: {bottom: 41, mid: 25, top: 16}}

and I'm trying to convert to something like this:

obj2 = 
{group: "A", bottom: "63", mid: "4", top: "15"}
{group: "B", bottom: "30", mid: "23", top: "5"}
{group: "C", bottom: "41", mid: "25", top: "16"}

by following this post but I'm getting an error obj1[key].forEach is not a function any ideas why I'm getting this error?

this is the code I'm using which is basically the same from the original:

obj1 ={A: {bottom: 63, mid: 4, top: 15}, B: {bottom: 30, mid: 23, top: 5}, C: {bottom: 41, mid: 25, top: 16}}

const result = []

// for each key in obj
Object.keys(obj1).forEach(key => {
    // for each array element of the property obj[key]
    obj1[key].forEach((value, index) => {// in this line I'm getting the error
        // if an object doesn't exists at the current index in result
        // create it
        if (!result[index]) {
            result[index] = {}
        }
        // at the result index, set the key to the current value
        result[index][key] = value
    })
})
console.log(result)

Answer 1

You are getting error because of this line obj1[key].forEach((value, index), because it is an object and you are trying to use forEach on an object.

For example obj1[key] will give the value of A and B etc keys which as an object like {bottom: 63, mid: 4, top: 15}.

You can us only for..in and then use destructing to push the values in the array

const obj1 = {
  A: {
    bottom: 63,
    mid: 4,
    top: 15
  },
  B: {
    bottom: 30,
    mid: 23,
    top: 5
  },
  C: {
    bottom: 41,
    mid: 25,
    top: 16
  }
}

const result = []

for (let key in obj1) {
  result.push(Object.assign({}, obj1[key], {
    group: key
  }))

}

console.log(result)

Answer 2

forEach is available on arrays, but during the first iteration obj1[key] is effectively obj1.A, which returns an object {bottom: 63, mid: 4, top: 15}, which doesn't have forEach, hence the error.

This might be a good use of reduce:

obj1 = {A: {bottom: 63, mid: 4, top: 15}, B: {bottom: 30, mid: 23, top: 5}, C: {bottom: 41, mid: 25, top: 16}}

const result = Object.entries(obj1).reduce(
  // group is the key from obj1, e.g. "A"
  // properties is the object for that key, e.g. { bottom: 63, mid: 4, top: 15 }
  (acc, [group, properties]) => [
    ...acc, { group, ...properties }
  ], []
);

console.log(result);