public/assets/knockout-3-4-0/src/binding/selectExtensions.js

   1 (function () {
   2     var hasDomDataExpandoProperty = '__ko__hasDomDataOptionValue__';
   3
   4     // Normally, SELECT elements and their OPTIONs can only take value of type 'string' (because the values
   5     // are stored on DOM attributes). ko.selectExtensions provides a way for SELECTs/OPTIONs to have values
   6     // that are arbitrary objects. This is very convenient when implementing things like cascading dropdowns.
   7     ko.selectExtensions = {
   8         readValue : function(element) {
   9             switch (ko.utils.tagNameLower(element)) {
  10                 case 'option':
  11                     if (element[hasDomDataExpandoProperty] === true)
  12                         return ko.utils.domData.get(element, ko.bindingHandlers.options.optionValueDomDataKey);
  13                     return ko.utils.ieVersion <= 7
  14                         ? (element.getAttributeNode('value') && element.getAttributeNode('value').specified ? element.value : element.text)
  15                         : element.value;
  16                 case 'select':
  17                     return element.selectedIndex >= 0 ? ko.selectExtensions.readValue(element.options[element.selectedIndex]) : undefined;
  18                 default:
  19                     return element.value;
  20             }
  21         },
  22
  23         writeValue: function(element, value, allowUnset) {
  24             switch (ko.utils.tagNameLower(element)) {
  25                 case 'option':
  26                     switch(typeof value) {
  27                         case "string":
  28                             ko.utils.domData.set(element, ko.bindingHandlers.options.optionValueDomDataKey, undefined);
  29                             if (hasDomDataExpandoProperty in element) { // IE <= 8 throws errors if you delete non-existent properties from a DOM node
  30                                 delete element[hasDomDataExpandoProperty];
  31                             }
  32                             element.value = value;
  33                             break;
  34                         default:
  35                             // Store arbitrary object using DomData
  36                             ko.utils.domData.set(element, ko.bindingHandlers.options.optionValueDomDataKey, value);
  37                             element[hasDomDataExpandoProperty] = true;
  38
  39                             // Special treatment of numbers is just for backward compatibility. KO 1.2.1 wrote numerical values to element.value.
  40                             element.value = typeof value === "number" ? value : "";
  41                             break;
  42                     }
  43                     break;
  44                 case 'select':
  45                     if (value === "" || value === null)       // A blank string or null value will select the caption
  46                         value = undefined;
  47                     var selection = -1;
  48                     for (var i = 0, n = element.options.length, optionValue; i < n; ++i) {
  49                         optionValue = ko.selectExtensions.readValue(element.options[i]);
  50                         // Include special check to handle selecting a caption with a blank string value
  51                         if (optionValue == value || (optionValue == "" && value === undefined)) {
  52                             selection = i;
  53                             break;
  54                         }
  55                     }
  56                     if (allowUnset || selection >= 0 || (value === undefined && element.size > 1)) {
  57                         element.selectedIndex = selection;
  58                     }
  59                     break;
  60                 default:
  61                     if ((value === null) || (value === undefined))
  62                         value = "";
  63                     element.value = value;
  64                     break;
  65             }
  66         }
  67     };
  68 })();
  69
  70 ko.exportSymbol('selectExtensions', ko.selectExtensions);
  71 ko.exportSymbol('selectExtensions.readValue', ko.selectExtensions.readValue);
  72 ko.exportSymbol('selectExtensions.writeValue', ko.selectExtensions.writeValue);