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166
lib/knockout/src/binding/defaultBindings/options.js
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166
lib/knockout/src/binding/defaultBindings/options.js
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var captionPlaceholder = {};
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ko.bindingHandlers['options'] = {
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'init': function(element) {
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if (ko.utils.tagNameLower(element) !== "select")
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throw new Error("options binding applies only to SELECT elements");
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// Remove all existing <option>s.
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while (element.length > 0) {
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element.remove(0);
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}
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// Ensures that the binding processor doesn't try to bind the options
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return { 'controlsDescendantBindings': true };
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},
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'update': function (element, valueAccessor, allBindings) {
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function selectedOptions() {
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return ko.utils.arrayFilter(element.options, function (node) { return node.selected; });
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}
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var selectWasPreviouslyEmpty = element.length == 0,
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multiple = element.multiple,
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previousScrollTop = (!selectWasPreviouslyEmpty && multiple) ? element.scrollTop : null,
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unwrappedArray = ko.utils.unwrapObservable(valueAccessor()),
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valueAllowUnset = allBindings.get('valueAllowUnset') && allBindings['has']('value'),
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includeDestroyed = allBindings.get('optionsIncludeDestroyed'),
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arrayToDomNodeChildrenOptions = {},
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captionValue,
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filteredArray,
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previousSelectedValues = [];
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if (!valueAllowUnset) {
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if (multiple) {
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previousSelectedValues = ko.utils.arrayMap(selectedOptions(), ko.selectExtensions.readValue);
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} else if (element.selectedIndex >= 0) {
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previousSelectedValues.push(ko.selectExtensions.readValue(element.options[element.selectedIndex]));
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}
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}
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if (unwrappedArray) {
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if (typeof unwrappedArray.length == "undefined") // Coerce single value into array
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unwrappedArray = [unwrappedArray];
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// Filter out any entries marked as destroyed
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filteredArray = ko.utils.arrayFilter(unwrappedArray, function(item) {
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return includeDestroyed || item === undefined || item === null || !ko.utils.unwrapObservable(item['_destroy']);
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});
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// If caption is included, add it to the array
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if (allBindings['has']('optionsCaption')) {
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captionValue = ko.utils.unwrapObservable(allBindings.get('optionsCaption'));
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// If caption value is null or undefined, don't show a caption
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if (captionValue !== null && captionValue !== undefined) {
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filteredArray.unshift(captionPlaceholder);
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}
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}
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} else {
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// If a falsy value is provided (e.g. null), we'll simply empty the select element
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}
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function applyToObject(object, predicate, defaultValue) {
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var predicateType = typeof predicate;
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if (predicateType == "function") // Given a function; run it against the data value
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return predicate(object);
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else if (predicateType == "string") // Given a string; treat it as a property name on the data value
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return object[predicate];
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else // Given no optionsText arg; use the data value itself
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return defaultValue;
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}
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// The following functions can run at two different times:
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// The first is when the whole array is being updated directly from this binding handler.
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// The second is when an observable value for a specific array entry is updated.
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// oldOptions will be empty in the first case, but will be filled with the previously generated option in the second.
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var itemUpdate = false;
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function optionForArrayItem(arrayEntry, index, oldOptions) {
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if (oldOptions.length) {
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previousSelectedValues = !valueAllowUnset && oldOptions[0].selected ? [ ko.selectExtensions.readValue(oldOptions[0]) ] : [];
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itemUpdate = true;
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}
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var option = element.ownerDocument.createElement("option");
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if (arrayEntry === captionPlaceholder) {
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ko.utils.setTextContent(option, allBindings.get('optionsCaption'));
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ko.selectExtensions.writeValue(option, undefined);
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} else {
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// Apply a value to the option element
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var optionValue = applyToObject(arrayEntry, allBindings.get('optionsValue'), arrayEntry);
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ko.selectExtensions.writeValue(option, ko.utils.unwrapObservable(optionValue));
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// Apply some text to the option element
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var optionText = applyToObject(arrayEntry, allBindings.get('optionsText'), optionValue);
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ko.utils.setTextContent(option, optionText);
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}
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return [option];
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}
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// By using a beforeRemove callback, we delay the removal until after new items are added. This fixes a selection
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// problem in IE<=8 and Firefox. See https://github.com/knockout/knockout/issues/1208
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arrayToDomNodeChildrenOptions['beforeRemove'] =
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function (option) {
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element.removeChild(option);
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};
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function setSelectionCallback(arrayEntry, newOptions) {
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if (itemUpdate && valueAllowUnset) {
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// The model value is authoritative, so make sure its value is the one selected
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// There is no need to use dependencyDetection.ignore since setDomNodeChildrenFromArrayMapping does so already.
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ko.selectExtensions.writeValue(element, ko.utils.unwrapObservable(allBindings.get('value')), true /* allowUnset */);
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} else if (previousSelectedValues.length) {
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// IE6 doesn't like us to assign selection to OPTION nodes before they're added to the document.
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// That's why we first added them without selection. Now it's time to set the selection.
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var isSelected = ko.utils.arrayIndexOf(previousSelectedValues, ko.selectExtensions.readValue(newOptions[0])) >= 0;
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ko.utils.setOptionNodeSelectionState(newOptions[0], isSelected);
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// If this option was changed from being selected during a single-item update, notify the change
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if (itemUpdate && !isSelected) {
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ko.dependencyDetection.ignore(ko.utils.triggerEvent, null, [element, "change"]);
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}
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}
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}
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var callback = setSelectionCallback;
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if (allBindings['has']('optionsAfterRender') && typeof allBindings.get('optionsAfterRender') == "function") {
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callback = function(arrayEntry, newOptions) {
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setSelectionCallback(arrayEntry, newOptions);
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ko.dependencyDetection.ignore(allBindings.get('optionsAfterRender'), null, [newOptions[0], arrayEntry !== captionPlaceholder ? arrayEntry : undefined]);
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}
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}
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ko.utils.setDomNodeChildrenFromArrayMapping(element, filteredArray, optionForArrayItem, arrayToDomNodeChildrenOptions, callback);
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ko.dependencyDetection.ignore(function () {
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if (valueAllowUnset) {
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// The model value is authoritative, so make sure its value is the one selected
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ko.selectExtensions.writeValue(element, ko.utils.unwrapObservable(allBindings.get('value')), true /* allowUnset */);
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} else {
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// Determine if the selection has changed as a result of updating the options list
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var selectionChanged;
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if (multiple) {
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// For a multiple-select box, compare the new selection count to the previous one
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// But if nothing was selected before, the selection can't have changed
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selectionChanged = previousSelectedValues.length && selectedOptions().length < previousSelectedValues.length;
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} else {
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// For a single-select box, compare the current value to the previous value
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// But if nothing was selected before or nothing is selected now, just look for a change in selection
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selectionChanged = (previousSelectedValues.length && element.selectedIndex >= 0)
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? (ko.selectExtensions.readValue(element.options[element.selectedIndex]) !== previousSelectedValues[0])
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: (previousSelectedValues.length || element.selectedIndex >= 0);
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}
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// Ensure consistency between model value and selected option.
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// If the dropdown was changed so that selection is no longer the same,
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// notify the value or selectedOptions binding.
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if (selectionChanged) {
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ko.utils.triggerEvent(element, "change");
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}
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}
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});
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// Workaround for IE bug
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ko.utils.ensureSelectElementIsRenderedCorrectly(element);
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if (previousScrollTop && Math.abs(previousScrollTop - element.scrollTop) > 20)
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element.scrollTop = previousScrollTop;
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}
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};
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ko.bindingHandlers['options'].optionValueDomDataKey = ko.utils.domData.nextKey();
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