extracting non-repeated keys from a data list

file.js

// Given a set of data where the keys of the objects can vary

const data = [
    { name: 'Amanda', email: 'amanda@example.com', genre: 'Female' },
    { name: 'Daniel', email: 'daniel@example.com', genre: 'Male', telephones: ['8989 7667', '8765 4321'] },
    { name: 'Arnulfo', email: 'arnulfo@example.com', genre: 'Male',  },
    { name: 'Ricardo', email: 'ricardo@example.com', genre: 'Male', city: 'Leon' },
    { name: 'Mario', genre: 'Male', single: true },
];

// Waiting for the next result: [ 'name', 'email', 'genre', 'telephones', 'city', 'single' ]

const result = data.reduce((accumulator, currentValue, index, self) => {
    if (index === 0) accumulator.push(...Object.keys(currentValue));
        
    const keys = Object.keys(currentValue).filter(key => accumulator.indexOf(key) === -1);

    accumulator.push(...keys);

    return accumulator;
}, []);

console.assert([ 'name', 'email', 'genre', 'telephones', 'city', 'single' ].join() === result.join(), 'Do not match');