Remove knockout js bindings on cloned element

问题:

I am using the knockout js template binding functionality to render a collection of items to an element:

<script type="text/javascript">
    ko.applyBindings(new function () {
        this.childItems = [{ Text: "Test", ImageUrl: "Images/Image.png" }];
    });
</script>

<script type="text/html" id="template">
    <div class="childItem" data-bind="attr: { title: Text }">
        <img data-bind="attr: { src: ImageUrl }" />
    </div>
</script> 

<div class="childSelector" data-bind="template: { name: 'template', foreach: childItems }">
</div>

When clicked, the child items are cloned and placed into another element:

$(".childSelector").on("click", ".childItem", function () {
    var clone = $(this).clone()[0];
    ko.cleanNode(clone);
    $(".targetNode").append(clone);
});

The problem is that when the source data changes and the template is re-bound to the new data, the following error is thrown:

Uncaught Error: Unable to parse bindings. Message: ReferenceError: Text is not defined; Bindings value: attr: { title: Text }

I had found another post that suggested using ko.cleanNode(element) to remove knockout's bindings, however this has not resolved the issue in my case.

Is there a way to remove knockout's bindings on a cloned element to prevent this error when re-binding? If not I'll just "manually" clone the element by extracting the required data from the clicked element.

Here is a simple example of what I'm doing

回答1:

You can remove all knockout bindings from an element by traversing the DOM and removing the data-bind attributes and knockout comments.

Use removeDataBindings(clone); but first clean the node with ko.cleanNode(clone) to clear any event handlers.

var commentNodesHaveTextProperty = document.createComment("test").text === "<!--test-->";
var startCommentRegex = commentNodesHaveTextProperty ? /^<!--\s*ko(?:\s+(.+\s*\:[\s\S]*))?\s*-->$/ : /^\s*ko(?:\s+(.+\s*\:[\s\S]*))?\s*$/;
var endCommentRegex =   commentNodesHaveTextProperty ? /^<!--\s*\/ko\s*-->$/ : /^\s*\/ko\s*$/;

function isStartComment(node) {
    return (node.nodeType == 8) && (commentNodesHaveTextProperty ? node.text : node.nodeValue).match(startCommentRegex);
}

function isEndComment(node) {
    return (node.nodeType == 8) && (commentNodesHaveTextProperty ? node.text : node.nodeValue).match(endCommentRegex);
}

function traverseNode(node, func) {
    func(node);
    node = node.firstChild;
    while (node) {
        traverseNode(node, func);
        node = node.nextSibling;
    }
}

function removeDataBindings(element) {
    var koComments = [];

    traverseNode(element, function (node) {
        if (isStartComment(node) || isEndComment(node)) {
            koComments.push(node);
            return;
        }
        //remove the 'data-bind' attributes
        if (node.nodeType === 1) { //ELEMENT_NODE
            node.removeAttribute('data-bind');
        }
    });

    //remove Knockout binding comments
    for (i = 0; i < koComments.length; i++) {
        node = koComments[i];
        if (node.parentNode) {
            node.parentNode.removeChild(node);
        }
    }
}

回答2:

Oliver, using jQuery to clone elements bound to knockout like this is not a good idea. You should be using data-binding for the targetNode. If you haven't yet done so, its a good idea to go through the Knockout Tutorials to get a good understanding of the basic uses.

If you are trying to keep a list of items, with a clone button, here is a dead simple fiddle using nothing but Knockout to do so. If you are trying to do something else, let me know; your question isn't entirely clear on your goal.

HTML:

<div data-bind="foreach: items">
    <span data-bind="text: $data"></span>
    <button data-bind="click: $parent.clone">Clone</button></br>
</div>

JS:

var ViewModel = function(data) {
    var self  = this;
    self.items = ko.observableArray(data);
    self.clone = function(item) {
        //The ko.toJS here is a handy copy tool for viewModels
        //It isn't necessary for simple arrays like this one
        //But I included it because for an array of objects, you will want to use it
        self.items.push(ko.toJS(item));
    };
};