在knockout.js中使用computed函数和subscribe函数之间的主要区别是什么？
答案 0 :(得分：21)
计算的observable通常用于返回计算值。作为计算评估的一部分访问的任何可观察对象（或其他计算机）将成为依赖关系并触发它再次运行。计算可以像订阅一样使用，当您想要一次订阅多个observable时，它尤其有用。但是，您不会知道哪个依赖项触发了更改。
手动订阅特定于单个可观察（或计算），并将新值作为其第一个参数传递。在订阅处理程序的执行中没有创建依赖关系的概念，因为只有在此可观察的更改时才会触发它。
答案 1 :(得分：8)
简而言之，计算类似于getter / setter属性，主要用于计算值。订阅是一种回调函数，您可以在subscribable对象中添加/删除，其中可观察和计算源派生自。
默认情况下，订阅会订阅一个名为“更改”的主题，并在明确定义时显示如下：
var obs = ko.observable();
obs.subscribe(function(newValue) { ... }, null, 'change');
您可以订阅另一个内置主题，称为'beforeChange'，传入的值是旧值：
obs.subscribe(function(oldValue) { ... }, null, 'beforeChange');
如果您愿意，还可以创建自己的自定义主题进行观看和“发布”，如下所示：
obs.subscribe(function(newValue) { ... }, null, 'customTopic');
obs("Hello World");// When this updates, 'change' and 'beforeChange' subscriptions are called.
obs.notifySubscribers('customTopic');// This is 'publishing' the new value to anyone subscribing to this topic.
Ryan Niemeyer在16:35有一个很棒的video以及基于这个概念的Knockout-Postbox插件。
答案 2 :(得分：2)
计算器运行依赖项以生成可绑定的新值。订阅功能就像一个事件。
答案 3 :(得分：-6)
使用它开始工作：）
function drawChart() {
var sample_data = document.getElementById('sample_data').value;
var data2 = eval("["+sample_data+"]");
var data = new google.visualization.arrayToDataTable(data2);
var options = {
hAxis: {title: 'Age', minValue: 0,maxValue:105},
vAxis: {title:'Savings', minValue: 0,maxValue:2500000},
width: 960, height: 300,
colors: ['#4a82bd'],
legend:'none'
};
var chart = new google.visualization.AreaChart(document.getElementById('chart_div'));
chart.draw(data, options);
}
google.load("visualization", "1", {packages:["corechart"]});
google.setOnLoadCallback(drawChart);
function buffer(){
setTimeout(function () {drawChart();}, 100);
}
function ViewModel() {
var self =this;
self.rangeSelect = ko.observable('0%');
self.dataGetter = ko.computed(function(){
var range = self.rangeSelect();
if(range=='0%'){
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if(range=='30%'){
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}
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}
if(range=='60%'){
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;
}
if(range=='70%'){
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}
});
}
//Activate knockout.js
ko.applyBindings(new ViewModel());
$(document).ready(function(){
$("input[name='range']").change(function(){
buffer();
});
})
这是一个更新的小提琴：http://jsfiddle.net/a_miguel6687/aL73X/6/