list.stream.js

var Bacon  = require('baconjs').Bacon,
    _      = require('underscore'),
    add    = new Bacon.Bus,
    remove = new Bacon.Bus,
    compose = function(fn) {
        return function (val) {
            return function(ctx) {
                return fn(ctx, val);
            }
        }
    },
    concat = function(arr, val) {
        return arr.concat(val);
    },
    list   = add
                .map(compose(concat)) // --> concat(list, val);
                .merge(remove.map(compose(_.without)))
                .scan([], function(list, op) {
                    return op(list);
                });

list.onValue(console.log);

add.push("a");
add.push("b");
add.push("c");

remove.push("b");

// outputs

[]
[ 'a' ]
[ 'a', 'b' ]
[ 'a', 'b', 'c' ]
[ 'a', 'c' ]