React JSX: rendering nested arrays of objects

Answer 1

You are not returning the JSX from your map method. Once you return the JSX you formed :

policyLegend.map(function(policy) {
              return (<div>
                <h3 key={ policy.id }>{ policy.displayName }</h3>
                {
                  policy.values.map(value => {
                    return(
                      <Form.Field key={ value.name }>
                        <label>{ value.displayName }</label>
                        <Checkbox toggle />
                      </Form.Field>
                    );
                  })
                }
              </div>)
            })

You should get the result you're looking for

Answer 2

It's because you do not return anything inside the policyLegend map. Try this:

{
    policyLegend.map((policy) => {
        return (
            <div>
                <h3 key={ policy.id }>{ policy.displayName }</h3>
                {
                    policy.values.map(value => {
                        return(
                            <Form.Field key={ value.name }>
                                <label>{ value.displayName }</label>
                                <Checkbox toggle />
                            </Form.Field>
                        );
                    })
                }
            </div>
        );
    })
}