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KnockoutJS: fades out after something else disappears

Let's say I have a set of 3 switches:

<div>
    <label>
        <input type="radio" name="Who" value="Myself" 
            checked="@isMyselfChecked" data-bind="checked: who" />
        Mine
    </label>
    <label>
        <input type="radio" name="Who" value="MemberId" 
            checked="@isMemberIdChecked" data-bind="checked: who" />
        I know the member ID
    </label>
    <label>
        <input type="radio" name="Who" value="MemberUrl" 
            checked="@isMemberUrlChecked" data-bind="checked: who" />
        I know the member URL
    </label>
</div>

When the user selects the first switch (Mine / Myself), an additional input is not required. However, when choosing the second or third, an additional input is required:

<div>
    <input type="text" name="MemberId" placeholder="Enter Member ID" 
        data-bind="toggleWho: who()" style="display: none" />
    <input type="text" name="MemberUrl" placeholder="Enter Member URL" 
        data-bind="toggleWho: who()" style="display: none; width: 450px;" />
</div>

It’s enough just to have data-bind="visible: who() === '[MemberId|MemberUrl]'"in dependent text fields. However, what if I want to add fade in / out transitions?

I tried a custom example fadeVisible bindingHandlerfrom a knockout site and I understand how it works. However, this will fade in and out in text boxes. If you select the radio 'MemberId', and the user selects the radio 'MemberUrl', I want to make the text box MemberIdhave disappeared before the text box MemberUrldisappear.

, , , , . , , ? ko.observale , , ko.computed?

var viewModel = {
    fadeSpeed: 150,
    who: ko.observable($('input[type=radio][name=Who]:checked').val())
};

ko.bindingHandlers.toggleWho = {
    init: function (element, valueAccessor) {
        var value = valueAccessor();
        var unwrapped = ko.utils.unwrapObservable(value);
        if (unwrapped === element.name)
            $(element).show();
    },
    update: function (element, valueAccessor) {
        var value = valueAccessor();
        var unwrapped = ko.utils.unwrapObservable(value);

        // when selected value is myself, fade out the visible one, if any
        if (unwrapped === 'Myself') {
            $('input[type=text][name=MemberId]:visible')
                .fadeOut(viewModel.fadeSpeed);
            $('input[type=text][name=MemberUrl]:visible')
                .fadeOut(viewModel.fadeSpeed);
        }

            // when selected value is memberid, may need to fade out url first
        else if (unwrapped === 'MemberId') {
            if ($('input[type=text][name=MemberUrl]:visible').length > 0) {
                $('input[type=text][name=MemberUrl]:visible')
                    .fadeOut(viewModel.fadeSpeed, function () {
                        $('input[type=text][name=MemberId]')
                            .fadeIn(viewModel.fadeSpeed);
                    });
            } else {
                $('input[type=text][name=MemberId]')
                    .fadeIn(viewModel.fadeSpeed);
            }
        }

            // when selected value is memberurl, may need to fade out id first
        else if (unwrapped === 'MemberUrl') {
            if ($('input[type=text][name=MemberId]:visible').length > 0) {
                $('input[type=text][name=MemberId]:visible')
                    .fadeOut(viewModel.fadeSpeed, function () {
                        $('input[type=text][name=MemberUrl]')
                            .fadeIn(viewModel.fadeSpeed);
                });
            } else {
                $('input[type=text][name=MemberUrl]')
                    .fadeIn(viewModel.fadeSpeed);
            }
        }
    }
};

ko.applyBindings(viewModel);
+5
3

, , .

:

var previousElement = null;
ko.bindingHandlers.fadeSwitcher = {
    init: function(element, valueAccessor) {
        var value = valueAccessor();
        $(element).toggle(ko.utils.unwrapObservable(value));
    },
    update: function(element, valueAccessor) {

        var value = ko.utils.unwrapObservable(valueAccessor());
        if (value) {
            if (previousElement == null) { // initial fade
                $(element).fadeIn();
            } else {
                $(previousElement).fadeOut('fast', function() {
                    $(element).fadeIn();
                });
            }
            previousElement = element;
        }        
    }
};
+9

, , , - .

, ; fadeOut/fadeIn / , .

Usage example: <span data-bind="fadeSwitcher: myObservable"></span>

ko.bindingHandlers.fadeSwitcher = {
    init: function (element, valueAccessor) {
        var value = ko.utils.unwrapObservable(valueAccessor());
        element.setAttribute('previousValue', value);
        ko.bindingHandlers.text.update(element, ko.observable(value));
    },
    update: function (element, valueAccessor) {
        var value = ko.utils.unwrapObservable(valueAccessor());
        var previousValue = element.getAttribute('previousValue');
        if (value !== previousValue) {
            $(element).fadeOut('fast', function () {
                ko.bindingHandlers.text.update(element, ko.observable(value));
                $(element).fadeIn();
            });
            element.setAttribute('previousValue', value);
        }
    }
};
+1

Thanks Tirius for the answer. I had to adapt it to the violin. I was able to use the slightly modified binding to make it work with the same radio stations as in the question (without preview):

@* radios same as in question *@
<div>
    <input type="text" name="MemberId" placeholder="Enter Member ID" 
        data-bind="whoFader: who() === 'MemberId'" style="display: none" />
    <input type="text" name="MemberUrl" placeholder="Enter Member URL" 
        data-bind="whoFader: who() === 'MemberUrl'" 
        style="display: none; width: 450px;" />
</div>

ko.bindingHandlers.whoFader = {
    previousElement: null,
    init: function (element, valueAccessor) {
        var value = valueAccessor();
        $(element).toggle(ko.utils.unwrapObservable(value));
    },
    update: function (element, valueAccessor) {
        var value = ko.utils.unwrapObservable(valueAccessor());
        if (value) {
            if (this.previousElement == null) {
                $(element).fadeIn('fast');
            } else {
                $(this.previousElement).hide();
                $(element).fadeIn('fast');
            }
            this.previousElement = element;
        }
        else {
            $(element).fadeOut('fast');
        }
    }
};
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