underscore js move throught two objects code example

Example 1: underscore js join

_.reduce(['x', 'y', 'z'], function(accumulator, currentItem) {
    return accumulator + currentItem;
});
// xyz

Example 2: Underscore.js

var evens = _.filter([1, 2, 3, 4, 5, 6], function(num){ return num % 2 == 0; });
=> [2, 4, 6]