underscore_query1.js

//this is row data coming from db
var dataset = [{
    firstname: 'John',
    lastname: 'Doe',
    birth: '1986-02-09',
    languages: ['en'],
    sex: 'm'
}, {
    firstname: 'Maria',
    lastname: 'Rossi',
    birth: '1982-03-05',
    languages: ['it', 'es'],
    sex: 'f'
}, {
    firstname: 'Enrique',
    lastname: 'Morales',
    birth: '1990-06-10',
    languages: ['en', 'es'],
    sex: 'm'
}];

//new_dataset is a new set of data which:
// - contains only spanish-speakers
// - is formatted with name, age and sex (as long text)
// - is ordered by age ascending
var new_dataset = _(dataset).chain()
    //after this, dataset will contain only spanish-speaker
    .filter(function(e) {
        return e.languages.indexOf('es') >= 0;
    })
    // after this, fileds will be formatted
    .map(function(e) {
        return {
            name: [e.firstname, e.lastname].join(' '),
            age: (function(birthday) {
                var ageDifMs = Date.now() - birthday.getTime();
                var ageDate = new Date(ageDifMs);
                return Math.abs(ageDate.getUTCFullYear() - 1970);
            })(new Date(e.birth)),
            sex: e.sex == 'm' ? 'Male' : 'Female'
        };
    })
    //after this, elements will be ordered
    .sortBy('age')
//this runs the chain
.value();

console.log(new_dataset);