TypeError: Cannot read property 'reduce' of undefined in react

I have a form in which I am asking the user to input field values for a couple of fields, storing the field values in an state and displaying the state values in a customised format.

So, I have a couple of input fields and a submit button:

<button onClick={this.handleSubmit}>Submit</button>
         {
           this.state.credentials &&
           //<Credentials value={this.state}/>
            <Credentials value={JSON.stringify(this.state, undefined, 2)} />
         }

The Credentials function convert the state of the component in JSON format:

const Credentials = ({value} ) => {
    return <pre>{formatState(value)}</pre>;
}

The formatState function will basically manipulate the state values and display them in the way I want:

function formatState(state) {
  console.log("hi")
  console.log(state);
    const output = state.groups.reduce((final, s)=> {
      console.log(output)
      const values = Object.keys(s).reduce((out, o)=> {
        out[o] = s[o].map(k => Object.values(k))
        return out;
        }, {})
        final =  {...final, ...values}
        return final;
      }, {})
      console.log(output) 
  }

The state looks like this:

{
  "groups": [
    {
      "typeA": [
        {
          "name": "abc"
        },
        {
          "number": "13,14"
        }
      ],
      "typeB": [
        {
          "country": "xyz"
        },
        {
          "date1": "2019-05-14"
        }
      ]
    }
  ]
}

But I want the output like this:

groups: {
"typeA": [[abc],[13,14]],
"typeB": [[2019-05-14],[xyz]]
}

SO, reduce function is used to convert the state into the following output. But I getting the error : "TypeError: Cannot read property 'reduce' of undefined"

Please can anybody tell me why this is happening.