[JS]KnockoutJS 3.0 Upgrade Noteを読む 第1弾 ref: http://qiita.com/tenntenn/items/954c7b48fe4b1ca8a368

2.3.0.dependentObservable.js

function evaluateImmediate() {
    //...
    // ここで値の更新と通知している
    dependentObservable["notifySubscribers"](_latestValue, "beforeChange");
    _latestValue = newValue;
    dependentObservable["notifySubscribers"](_latestValue);
    //...
}

3.0.0.dependentObservable.js

function evaluateImmediate() {
    //...
    // 変更なければ、更新も通知もしない
    if (!dependentObservable['equalityComparer'] || !dependentObservable['equalityComparer'](_latestValue, newValue)) {
        dependentObservable["notifySubscribers"](_latestValue, "beforeChange");
        _latestValue = newValue;
        dependentObservable["notifySubscribers"](_latestValue);
    }
    //...
}

file2.js

var n = ko.observable(10);

var evenN = ko.computed(function() {
    var isEven = n() % 2 == 0;
    alert(isEven);
    console.log(isEven);
    return isEven;
});

evenN.subscribe(function(newValue) {
    alert("change evenN to " + newValue);
    console.log("change evenN to " + newValue);
});

n(20);
n(21);

file3.js

var n = ko.observable(10);

var evenN = ko.computed(function() {
    var isEven = n() % 2 == 0;
    alert(isEven);
    console.log(isEven);
    return isEven;
});

// 必ず通知がいくようにする
evenN.extend({notify: 'always'});

evenN.subscribe(function(newValue) {
    alert("change evenN to " + newValue);
    console.log("change evenN to " + newValue);
});

n(20);
n(21);