knockout check/uncheck all combo box

问题:

I using knockout for mapping JSON obejct to user control, I have a list of single checkboxes, They look like

 <input type="checkbox" data-bind="checked: IsEnabled1" />

I Have JsonObject

 var viewModel = {
            IsEnabled1 :ko.observable(true),            
            IsEnabled2 :ko.observable(true),
            IsEnabled3 :ko.observable(false)
        };
  ...
  ko.applyBindings(viewModel);

And I want to add global check box that will be check/uncheck all other, I made this changes on JavaScript side but global check box update UI part but they data from separate check boxes doesn't mapping to JSON object .

Global checkbox

  $("#GeneralTable thead tr th:first input:checkbox").click(function () {
            var checkedStatus = this.checked;
            $("#GeneralTable tbody tr td:first-child input:checkbox").each(function () {
                this.checked = checkedStatus;                    
            });

        });

after this code my JSON object contain data that not related to UI.

How to update all JSON after change check boxes from JS side ?

回答1:

Please check the example: http://jsfiddle.net/MenukaIshan/5gaLjh2c/

I think it is exactly what you need. All items have IsChecked observable property. ViewModel contains computed observable (readable and writeable) to check or uncheck all items.

回答2:

There is an alternative solution here http://jsfiddle.net/rniemeyer/kXYuU/

The solution above can be improved in two ways

-To make AllChecked false for empty lists, we need to check length

-To reduce the number recalculations when selecting all for a long list, we need to add throttle

self.AllChecked = ko.computed({
    read: function() {
        var firstUnchecked = ko.utils.arrayFirst(self.Items, function(item) {
            return item.IsChecked() == false;
        });
        return self.Items.length && !firstUnchecked;
    },
    write: function(value) {
        ko.utils.arrayForEach(self.Items, function(item) {
            item.IsChecked(value);
        });
    }
}).extend({ throttle: 1 });