Edit in JSFiddle

var records = [
    {
        data: {},
    },
    {
        user: {
            name: 'Horacek',
            email: '[email protected]',
        },
        data: {},
    },
    {
        user: {
            name: 'Mach',
        },
        data: {},
    },
    {
        data: {},
    },
    {
        user: {
            name: 'Pazout',
            email: '[email protected]',
        },
        data: {},
    }
];

var emails = _(records).filter('user').map('user').filter('email').map('email').value();
document.getElementById('demo').innerHTML = emails;

<p id="demo"></p>