ES3 Observable

computed.js

var Observable = require("./index.js")

module.exports = computed

function computed(observables, lambda) {
    var values = []

    function listener(i) {
        return function (value) {
            values[i] = value
            result.set(lambda.apply(null, values))
        };
    }

    for (var i = 0, len = observables.length; i < len; i++) {
        values.push(observables[i]())
        observables[i](listener(i))
    }

    var result = Observable(lambda.apply(null, values))

    return result
}

index.js

module.exports = Observable

function Observable(value) {
    var listeners = []
    value = value === undefined ? null : value

    observable.set = function (v) {
        value = v
        
        for (var i = 0, len = listeners.length; i < len; i++) {
            listeners[i](v)
        }
    }

    return observable

    function observable(listener) {
        if (!listener) {
            return value
        }

        listeners.push(listener)

        return function remove() {
            for (var i = 0, len = listeners.length; i < len; i++) {
                if (listeners[i] === listener) {
                    listeners.splice(i, 1)
                    break
                }
            }
        }
    }
}