Can't get the most simple knockout.js sample t

2019-03-18 10:26发布

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问题:

This really bothers me. Please have a look at the Hello World example of knockout.js.

Here is my code:

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>Home Page</title>
    <script src="knockout-1.2.1.debug.js" type="text/javascript"></script>

    <script type="text/javascript">
        // Here's my data model
        var viewModel = {
            firstName: ko.observable("Planet"),
            lastName: ko.observable("Earth")
        };
        viewModel.fullName = ko.dependentObservable(function () {
            // Knockout tracks dependencies automatically. It knows that fullName depends on firstName and lastName, because these get called when evaluating fullName.
            return viewModel.firstName() + " " + viewModel.lastName();
        });

        ko.applyBindings(viewModel); // This makes Knockout get to work
    </script>

</head>
<body>
    <p>First name: <input data-bind="value: firstName" /></p>
    <p>Last name: <input data-bind="value: lastName" /></p>
    <h2>Hello, <span data-bind="text: fullName"> </span>!</h2>
</body>
</html>

It seems, that the binding doesn't work. If I alert(viewModel.fullName()); I get "Planet Earth" as expected. But neither the input elements nor the span gets filled with data.

What am I doing wrong?

Here is a zip file which includes both my file and knockout.js

回答1:

Your issue is that you are calling ko.applyBindings too soon.

You want to either move your script tag to the bottom or execute it in an onload or something like jQuery's ready function.



回答2:

Just add window.onload= function() in the beginning of script..

  window.onload= function() {

    // Here's my data model
    var viewModel = {
......
    ko.applyBindings(viewModel); // This makes Knockout get to work
  }
</script>


回答3:

This is a working version of the KnockoutJs tutorial.

 <!DOCTYPE html>
<html>
<head>

    <link rel="stylesheet" type="text/css" href="style/monitor.css">
    <script type="text/javascript" src="js/knockout-2.3.0.js"></script>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
    <script type="text/javascript">
        function WebmailViewModel() {
            // Data
            var self = this;
            self.folders = [ 'Inbox', 'Archive', 'Sent', 'Spam' ];
            self.chosenFolderId = ko.observable();
            self.chosenFolderData = ko.observable();
            self.chosenMailData = ko.observable();

            // Behaviours    
            self.goToFolder = function(folder) {
                self.chosenFolderId(folder);
                self.chosenMailData(null); // Stop showing a mail
                $.get('/mail', {
                    folder : folder
                }, self.chosenFolderData);
            };
            self.goToMail = function(mail) {
                self.chosenFolderId(mail.folder);
                self.chosenFolderData(null); // Stop showing a folder
                $.get("/mail", {
                    mailId : mail.id
                }, self.chosenMailData);
            };

            // Show inbox by default
            self.goToFolder('Archive');
        };


    </script>
</head>
<body onload="ko.applyBindings(new WebmailViewModel());">
    <!-- Folders -->
    <ul data-bind="foreach: folders">
        <li>
            The current folders are: <b data-bind="text: $data"></b>
        </li>
    </ul>   
    </body>
    </html>


回答4:

The ko.applyBindings() should called once the view gets loaded then the data gets binded to the controls automatically.



回答5:

Looking at the demos for knockout.js, you're missing one thing. You're not sending the view model as a parameter in to the dependentObservable function:

viewModel.fullName = ko.dependentObservable(function () {
        // Knockout tracks dependencies automatically. It knows that fullName depends on firstName and lastName, because these get called when evaluating fullName.
        return viewModel.firstName() + " " + viewModel.lastName();
    }, viewModel);


回答6:

If the values are not binding just fire up a check functionality before you make use of the array. In knockout you can do this like 

< !-- ko if:detail() -->


   --your HTML code to display the fields goes here--


 <!-- /ko -->


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