Map-Reduce Example

gistfile1.js

var rows = ["alice apple", "bob banana", "charlie cherry", "alice date", "bob eggplant"];

var mapped = rows.map(function(row) {
    return row.split(" ");
});

var reduced = mapped.reduce(function(hash, pair) {
    var key = pair[0],
        val = pair[1];

    hash[key] ? hash[key].push(val) : hash[key] = [val]
    return hash;
}, {});

// {"alice": ["apple", "date"], "bob": ["banana", "eggplant"], "charlie": ["cherry"]}