this.varName = ko.computed(function(){ ... ... // function code ... },this);
<!DOCTYPE html>
<head >
<title>KnockoutJS Computed Observables</title>
<script src = "https://ajax.aspnetcdn.com/ajax/knockout/knockout-3.1.0.js"></script>
</head>
<body>
<p>Enter first number: <input data-bind = "value: a" /></p>
<p>Enter second number: <input data-bind = "value: b"/></p>
<p>Average := <span data-bind="text: totalAvg"></span></p>
<script>
function MyViewModel() {
this.a = ko.observable(10);
this.b = ko.observable(40);
this.totalAvg = ko.computed(function() {
if(typeof(this.a()) !== "number" || typeof(this.b()) !== "number") {
this.a(Number(this.a())); //convert string to Number
this.b(Number(this.b())); //convert string to Number
}
total = (this.a() + this.b())/2 ;
return total;
},this);
}
ko.applyBindings(new MyViewModel());
</script>
</body>
</html>
<p>Enter first number: <input data-bind = "value: a" /></p> <p>Enter second number: <input data-bind = "value: b"/></p> <p>Average := <span data-bind = "text: totalAvg"></span></p>
this.totalAvg = ko.computed(function() { if(typeof(this.a()) !== "number" || typeof(this.b()) !== "number") { this.a(Number(this.a())); //convert string to Number this.b(Number(this.b())); //convert string to Number } total = (this.a() + this.b())/2 ; return total; },this);
<p>Average := <span data-bind = "text: totalAvg"></span></p>
function MyViewModel(){
self = this;
self.a = ko.observable(10);
self.b = ko.observable(40);
this.totalAvg = ko.computed(function() {
if(typeof(self.a()) !== "number" || typeof(self.b()) !== "number") {
self.a(Number(self.a())); //convert string to Number
self.b(Number(self.b())); //convert string to Number
}
total = (self.a() + self.b())/2 ;
return total;
});
}
myViewModel.property = ko.pureComputed(function() { return ...; // code logic goes here }).extend({ notify: 'always' });
// make sure there are updates no more than once per 100-millisecond period myViewModel.property.extend({ rateLimit: 100 });
| Sr.No. | 功能 |
| 1 |
ko.isComputed
如果属性是计算可观察的，则返回
true。
|
| 2 |
ko.isObservable
如果属性是 Observable、Observable 数组或计算 Observable，则返回
true。
|
| 3 |
ko.isWritableObservable
如果 Observable、Observable 数组或 Writable Computed Observable，则返回
true。 （这也称为 ko.isWriteableObservable）
|
myViewModel.fullName('Tom Smith').age(45)
<!DOCTYPE html>
<head >
<title>KnockoutJS Writable Computed Observable</title>
<script src = "https://ajax.aspnetcdn.com/ajax/knockout/knockout-3.3.0.js"></script>
</head>
<body>
<p>Enter your birth Date: <input type = "date" data-bind = "value: rawDate" ></p>
<p><span data-bind = "text: yourAge"></span></p>
<script>
function MyViewModel() {
this.yourAge = ko.observable();
today = new Date();
rawDate = ko.observable();
this.rawDate = ko.pureComputed ({
read: function() {
return this.yourAge;
},
write: function(value) {
var b = Date.parse(value); // convert birth date into milliseconds
var t = Date.parse(today); // convert todays date into milliseconds
diff = t-b; // take difference
var y = Math.floor(diff/31449600000); // difference is converted
// into years. 31449600000
//milliseconds form a year.
var m = Math.floor((diff % 31449600000)/604800000/4.3); // calculating
// months.
// 604800000
// milliseconds
// form a week.
this.yourAge("You are " + y + " year(s) " + m +" months old.");
},
owner: this
});
}
ko.applyBindings(new MyViewModel());
</script>
</body>
</html>
