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Knockoutjs (version 2.1.0): bind boolean value to select box

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难免孤独
难免孤独 2020-12-09 16:19

I want to bind boolean value to select element using KO v2.1.0, but obviously it doesn\'t work as expected.

html code:
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  • 囚心锁ツ
    2020-12-09 16:44

    Here is an option that we explored for this one from this forum post: 

    ko.bindingHandlers.booleanValue = {
    init: function(element, valueAccessor, allBindingsAccessor) {
        var observable = valueAccessor(),
            interceptor = ko.computed({
                read: function() {
                    return observable().toString();
                },
                write: function(newValue) {
                    observable(newValue === "true");
                }                   
            });

        ko.applyBindingsToNode(element, { value: interceptor });
    }
};

    So, we use a custom binding to inject a writeable computed observable between the UI and our view model. This is just an alternative to doing it directly in your view model.

    Sample here: http://jsfiddle.net/rniemeyer/H4gpe/

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  • 孤街浪徒
    2020-12-09 16:47

    I think I got the answer, put the number "1" and "0" to the option value respectively:

    <select data-bind="value: state">
    <option value="1">On</option>
    <option value="0">Off</option>
</select>

    See http://jsfiddle.net/greenlaw110/Ajm58/2/

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  • 清酒与你
    2020-12-09 16:55

    This happens because the select is working with strings, and not booleans at any stage. You should try a ko.computed( ... ) value instead.

    Check here for details: http://jsfiddle.net/Ajm58/3/

    <select id="testSelect" data-bind="value: stateString">
    <option value="true">true</option>
    <option value="false">false</option>
</select>
​

var model = {
    state: ko.observable(false)
};

model.stateString = ko.computed({
    read: function() { return (this.state() ? "true" : "false"); },
    write: function(value) { this.state(value == "true"); }
}, model);

ko.applyBindings(model);


setTimeout(function() {
    model.state(true);    
}, 1500);

setTimeout(function() {
    $("#testSelect").val("false");
}, 3000);
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