ngRepeat.js

'use strict';

/**
 * @ngdoc directive
 * @name ngRepeat
 * @multiElement
 *
 * @description
 * The `ngRepeat` directive instantiates a template once per item from a collection. Each template
 * instance gets its own scope, where the given loop variable is set to the current collection item,
 * and `$index` is set to the item index or key.
 *
 * Special properties are exposed on the local scope of each template instance, including:
 *
 * | Variable  | Type            | Details                                                                     |
 * |-----------|-----------------|-----------------------------------------------------------------------------|
 * | `$index`  | {@type number}  | iterator offset of the repeated element (0..length-1)                       |
 * | `$first`  | {@type boolean} | true if the repeated element is first in the iterator.                      |
 * | `$middle` | {@type boolean} | true if the repeated element is between the first and last in the iterator. |
 * | `$last`   | {@type boolean} | true if the repeated element is last in the iterator.                       |
 * | `$even`   | {@type boolean} | true if the iterator position `$index` is even (otherwise false).           |
 * | `$odd`    | {@type boolean} | true if the iterator position `$index` is odd (otherwise false).            |
 *
 * Creating aliases for these properties is possible with {@link ng.directive:ngInit `ngInit`}.
 * This may be useful when, for instance, nesting ngRepeats.
 *
 *
 * # Iterating over object properties
 *
 * It is possible to get `ngRepeat` to iterate over the properties of an object using the following
 * syntax:
 *
 * ```js
 * <div ng-repeat="(key, value) in myObj"> ... </div>
 * ```
 *
 * You need to be aware that the JavaScript specification does not define the order of keys
 * returned for an object. (To mitigate this in Angular 1.3 the `ngRepeat` directive
 * used to sort the keys alphabetically.)
 *
 * Version 1.4 removed the alphabetic sorting. We now rely on the order returned by the browser
 * when running `for key in myObj`. It seems that browsers generally follow the strategy of providing
 * keys in the order in which they were defined, although there are exceptions when keys are deleted
 * and reinstated. See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete#Cross-browser_issues
 *
 * If this is not desired, the recommended workaround is to convert your object into an array
 * that is sorted into the order that you prefer before providing it to `ngRepeat`.  You could
 * do this with a filter such as [toArrayFilter](http://ngmodules.org/modules/angular-toArrayFilter)
 * or implement a `$watch` on the object yourself.
 *
 *
 * # Tracking and Duplicates
 *
 * When the contents of the collection change, `ngRepeat` makes the corresponding changes to the DOM:
 *
 * * When an item is added, a new instance of the template is added to the DOM.
 * * When an item is removed, its template instance is removed from the DOM.
 * * When items are reordered, their respective templates are reordered in the DOM.
 *
 * By default, `ngRepeat` does not allow duplicate items in arrays. This is because when
 * there are duplicates, it is not possible to maintain a one-to-one mapping between collection
 * items and DOM elements.
 *
 * If you do need to repeat duplicate items, you can substitute the default tracking behavior
 * with your own using the `track by` expression.
 *
 * For example, you may track items by the index of each item in the collection, using the
 * special scope property `$index`:
 * ```html
 *    <div ng-repeat="n in [42, 42, 43, 43] track by $index">
 *      {{n}}
 *    </div>
 * ```
 *
 * You may use arbitrary expressions in `track by`, including references to custom functions
 * on the scope:
 * ```html
 *    <div ng-repeat="n in [42, 42, 43, 43] track by myTrackingFunction(n)">
 *      {{n}}
 *    </div>
 * ```
 *
 * If you are working with objects that have an identifier property, you can track
 * by the identifier instead of the whole object. Should you reload your data later, `ngRepeat`
 * will not have to rebuild the DOM elements for items it has already rendered, even if the
 * JavaScript objects in the collection have been substituted for new ones:
 * ```html
 *    <div ng-repeat="model in collection track by model.id">
 *      {{model.name}}
 *    </div>
 * ```
 *
 * When no `track by` expression is provided, it is equivalent to tracking by the built-in
 * `$id` function, which tracks items by their identity:
 * ```html
 *    <div ng-repeat="obj in collection track by $id(obj)">
 *      {{obj.prop}}
 *    </div>
 * ```
 *
 * <div class="alert alert-warning">
 * **Note:** `track by` must always be the last expression:
 * </div>
 * ```
 * <div ng-repeat="model in collection | orderBy: 'id' as filtered_result track by model.id">
 *     {{model.name}}
 * </div>
 * ```
 *
 * # Special repeat start and end points
 * To repeat a series of elements instead of just one parent element, ngRepeat (as well as other ng directives) supports extending
 * the range of the repeater by defining explicit start and end points by using **ng-repeat-start** and **ng-repeat-end** respectively.
 * The **ng-repeat-start** directive works the same as **ng-repeat**, but will repeat all the HTML code (including the tag it's defined on)
 * up to and including the ending HTML tag where **ng-repeat-end** is placed.
 *
 * The example below makes use of this feature:
 * ```html
 *   <header ng-repeat-start="item in items">
 *     Header {{ item }}
 *   </header>
 *   <div class="body">
 *     Body {{ item }}
 *   </div>
 *   <footer ng-repeat-end>
 *     Footer {{ item }}
 *   </footer>
 * ```
 *
 * And with an input of {@type ['A','B']} for the items variable in the example above, the output will evaluate to:
 * ```html
 *   <header>
 *     Header A
 *   </header>
 *   <div class="body">
 *     Body A
 *   </div>
 *   <footer>
 *     Footer A
 *   </footer>
 *   <header>
 *     Header B
 *   </header>
 *   <div class="body">
 *     Body B
 *   </div>
 *   <footer>
 *     Footer B
 *   </footer>
 * ```
 *
 * The custom start and end points for ngRepeat also support all other HTML directive syntax flavors provided in AngularJS (such
 * as **data-ng-repeat-start**, **x-ng-repeat-start** and **ng:repeat-start**).
 *
 * @animations
 * `.ng-enter` - when a new item is added to the list or when an item is revealed after a filter
 *
 * `.ng-leave` - when an item is removed from the list or when an item is filtered out
 *
 * `.ng-move` - when an adjacent item is filtered out causing a reorder or when the item contents are reordered
 *
 * @element ANY
 * @scope
 * @priority 1000
 * @param {repeat_expression} ngRepeat The expression indicating how to enumerate a collection. These
 *   formats are currently supported:
 *
 *   * `variable in expression` – where variable is the user defined loop variable and `expression`
 *     is a scope expression giving the collection to enumerate.
 *
 *     For example: `album in artist.albums`.
 *
 *   * `(key, value) in expression` – where `key` and `value` can be any user defined identifiers,
 *     and `expression` is the scope expression giving the collection to enumerate.
 *
 *     For example: `(name, age) in {'adam':10, 'amalie':12}`.
 *
 *   * `variable in expression track by tracking_expression` – You can also provide an optional tracking expression
 *     which can be used to associate the objects in the collection with the DOM elements. If no tracking expression
 *     is specified, ng-repeat associates elements by identity. It is an error to have
 *     more than one tracking expression value resolve to the same key. (This would mean that two distinct objects are
 *     mapped to the same DOM element, which is not possible.)
 *
 *     Note that the tracking expression must come last, after any filters, and the alias expression.
 *
 *     For example: `item in items` is equivalent to `item in items track by $id(item)`. This implies that the DOM elements
 *     will be associated by item identity in the array.
 *
 *     For example: `item in items track by $id(item)`. A built in `$id()` function can be used to assign a unique
 *     `$$hashKey` property to each item in the array. This property is then used as a key to associated DOM elements
 *     with the corresponding item in the array by identity. Moving the same object in array would move the DOM
 *     element in the same way in the DOM.
 *
 *     For example: `item in items track by item.id` is a typical pattern when the items come from the database. In this
 *     case the object identity does not matter. Two objects are considered equivalent as long as their `id`
 *     property is same.
 *
 *     For example: `item in items | filter:searchText track by item.id` is a pattern that might be used to apply a filter
 *     to items in conjunction with a tracking expression.
 *
 *   * `variable in expression as alias_expression` – You can also provide an optional alias expression which will then store the
 *     intermediate results of the repeater after the filters have been applied. Typically this is used to render a special message
 *     when a filter is active on the repeater, but the filtered result set is empty.
 *
 *     For example: `item in items | filter:x as results` will store the fragment of the repeated items as `results`, but only after
 *     the items have been processed through the filter.
 *
 *     Please note that `as [variable name] is not an operator but rather a part of ngRepeat micro-syntax so it can be used only at the end
 *     (and not as operator, inside an expression).
 *
 *     For example: `item in items | filter : x | orderBy : order | limitTo : limit as results` .
 *
 * @example
 * This example initializes the scope to a list of names and
 * then uses `ngRepeat` to display every person:
  <example module="ngAnimate" deps="angular-animate.js" animations="true">
    <file name="index.html">
      <div ng-init="friends = [
        {name:'John', age:25, gender:'boy'},
        {name:'Jessie', age:30, gender:'girl'},
        {name:'Johanna', age:28, gender:'girl'},
        {name:'Joy', age:15, gender:'girl'},
        {name:'Mary', age:28, gender:'girl'},
        {name:'Peter', age:95, gender:'boy'},
        {name:'Sebastian', age:50, gender:'boy'},
        {name:'Erika', age:27, gender:'girl'},
        {name:'Patrick', age:40, gender:'boy'},
        {name:'Samantha', age:60, gender:'girl'}
      ]">
        I have {{friends.length}} friends. They are:
        <input type="search" ng-model="q" placeholder="filter friends..." aria-label="filter friends" />
        <ul class="example-animate-container">
          <li class="animate-repeat" ng-repeat="friend in friends | filter:q as results">
            [{{$index + 1}}] {{friend.name}} who is {{friend.age}} years old.
          </li>
          <li class="animate-repeat" ng-if="results.length == 0">
            <strong>No results found...</strong>
          </li>
        </ul>
      </div>
    </file>
    <file name="animations.css">
      .example-animate-container {
        background:white;
        border:1px solid black;
        list-style:none;
        margin:0;
        padding:0 10px;
      }

      .animate-repeat {
        line-height:40px;
        list-style:none;
        box-sizing:border-box;
      }

      .animate-repeat.ng-move,
      .animate-repeat.ng-enter,
      .animate-repeat.ng-leave {
        transition:all linear 0.5s;
      }

      .animate-repeat.ng-leave.ng-leave-active,
      .animate-repeat.ng-move,
      .animate-repeat.ng-enter {
        opacity:0;
        max-height:0;
      }

      .animate-repeat.ng-leave,
      .animate-repeat.ng-move.ng-move-active,
      .animate-repeat.ng-enter.ng-enter-active {
        opacity:1;
        max-height:40px;
      }
    </file>
    <file name="protractor.js" type="protractor">
      var friends = element.all(by.repeater('friend in friends'));

      it('should render initial data set', function() {
        expect(friends.count()).toBe(10);
        expect(friends.get(0).getText()).toEqual('[1] John who is 25 years old.');
        expect(friends.get(1).getText()).toEqual('[2] Jessie who is 30 years old.');
        expect(friends.last().getText()).toEqual('[10] Samantha who is 60 years old.');
        expect(element(by.binding('friends.length')).getText())
            .toMatch("I have 10 friends. They are:");
      });

       it('should update repeater when filter predicate changes', function() {
         expect(friends.count()).toBe(10);

         element(by.model('q')).sendKeys('ma');

         expect(friends.count()).toBe(2);
         expect(friends.get(0).getText()).toEqual('[1] Mary who is 28 years old.');
         expect(friends.last().getText()).toEqual('[2] Samantha who is 60 years old.');
       });
      </file>
    </example>
 */
var ngRepeatDirective = ['$parse', '$animate', function($parse, $animate) {
  var NG_REMOVED = '$$NG_REMOVED';
  var ngRepeatMinErr = minErr('ngRepeat');

  var updateScope = function(scope, index, valueIdentifier, value, keyIdentifier, key, arrayLength) {
    // TODO(perf): generate setters to shave off ~40ms or 1-1.5%
    scope[valueIdentifier] = value;
    if (keyIdentifier) scope[keyIdentifier] = key;
    scope.$index = index;
    scope.$first = (index === 0);
    scope.$last = (index === (arrayLength - 1));
    scope.$middle = !(scope.$first || scope.$last);
    // jshint bitwise: false
    scope.$odd = !(scope.$even = (index&1) === 0);
    // jshint bitwise: true
  };

  var getBlockStart = function(block) {
    return block.clone[0];
  };

  var getBlockEnd = function(block) {
    return block.clone[block.clone.length - 1];
  };


  return {
    restrict: 'A',
    multiElement: true,
    transclude: 'element',
    priority: 1000,
    terminal: true,
    $$tlb: true,
    compile: function ngRepeatCompile($element, $attr) {
      var expression = $attr.ngRepeat;
      var ngRepeatEndComment = document.createComment(' end ngRepeat: ' + expression + ' ');

      var match = expression.match(/^\s*([\s\S]+?)\s+in\s+([\s\S]+?)(?:\s+as\s+([\s\S]+?))?(?:\s+track\s+by\s+([\s\S]+?))?\s*$/);

      if (!match) {
        throw ngRepeatMinErr('iexp', "Expected expression in form of '_item_ in _collection_[ track by _id_]' but got '{0}'.",
            expression);
      }

      var lhs = match[1];
      var rhs = match[2];
      var aliasAs = match[3];
      var trackByExp = match[4];

      match = lhs.match(/^(?:(\s*[\$\w]+)|\(\s*([\$\w]+)\s*,\s*([\$\w]+)\s*\))$/);

      if (!match) {
        throw ngRepeatMinErr('iidexp', "'_item_' in '_item_ in _collection_' should be an identifier or '(_key_, _value_)' expression, but got '{0}'.",
            lhs);
      }
      var valueIdentifier = match[3] || match[1];
      var keyIdentifier = match[2];

      if (aliasAs && (!/^[$a-zA-Z_][$a-zA-Z0-9_]*$/.test(aliasAs) ||
          /^(null|undefined|this|\$index|\$first|\$middle|\$last|\$even|\$odd|\$parent|\$root|\$id)$/.test(aliasAs))) {
        throw ngRepeatMinErr('badident', "alias '{0}' is invalid --- must be a valid JS identifier which is not a reserved name.",
          aliasAs);
      }

      var trackByExpGetter, trackByIdExpFn, trackByIdArrayFn, trackByIdObjFn;
      var hashFnLocals = {$id: hashKey};

      if (trackByExp) {
        trackByExpGetter = $parse(trackByExp);
      } else {
        trackByIdArrayFn = function(key, value) {
          return hashKey(value);
        };
        trackByIdObjFn = function(key) {
          return key;
        };
      }

      return function ngRepeatLink($scope, $element, $attr, ctrl, $transclude) {

        if (trackByExpGetter) {
          trackByIdExpFn = function(key, value, index) {
            // assign key, value, and $index to the locals so that they can be used in hash functions
            if (keyIdentifier) hashFnLocals[keyIdentifier] = key;
            hashFnLocals[valueIdentifier] = value;
            hashFnLocals.$index = index;
            return trackByExpGetter($scope, hashFnLocals);
          };
        }

        // Store a list of elements from previous run. This is a hash where key is the item from the
        // iterator, and the value is objects with following properties.
        //   - scope: bound scope
        //   - element: previous element.
        //   - index: position
        //
        // We are using no-proto object so that we don't need to guard against inherited props via
        // hasOwnProperty.
        var lastBlockMap = createMap();

        //watch props
        $scope.$watchCollection(rhs, function ngRepeatAction(collection) {
          var index, length,
              previousNode = $element[0],     // node that cloned nodes should be inserted after
                                              // initialized to the comment node anchor
              nextNode,
              // Same as lastBlockMap but it has the current state. It will become the
              // lastBlockMap on the next iteration.
              nextBlockMap = createMap(),
              collectionLength,
              key, value, // key/value of iteration
              trackById,
              trackByIdFn,
              collectionKeys,
              block,       // last object information {scope, element, id}
              nextBlockOrder,
              elementsToRemove;

          if (aliasAs) {
            $scope[aliasAs] = collection;
          }

          if (isArrayLike(collection)) {
            collectionKeys = collection;
            trackByIdFn = trackByIdExpFn || trackByIdArrayFn;
          } else {
            trackByIdFn = trackByIdExpFn || trackByIdObjFn;
            // if object, extract keys, in enumeration order, unsorted
            collectionKeys = [];
            for (var itemKey in collection) {
              if (collection.hasOwnProperty(itemKey) && itemKey.charAt(0) !== '$') {
                collectionKeys.push(itemKey);
              }
            }
          }

          collectionLength = collectionKeys.length;
          nextBlockOrder = new Array(collectionLength);

          // locate existing items
          for (index = 0; index < collectionLength; index++) {
            key = (collection === collectionKeys) ? index : collectionKeys[index];
            value = collection[key];
            trackById = trackByIdFn(key, value, index);
            if (lastBlockMap[trackById]) {
              // found previously seen block
              block = lastBlockMap[trackById];
              delete lastBlockMap[trackById];
              nextBlockMap[trackById] = block;
              nextBlockOrder[index] = block;
            } else if (nextBlockMap[trackById]) {
              // if collision detected. restore lastBlockMap and throw an error
              forEach(nextBlockOrder, function(block) {
                if (block && block.scope) lastBlockMap[block.id] = block;
              });
              throw ngRepeatMinErr('dupes',
                  "Duplicates in a repeater are not allowed. Use 'track by' expression to specify unique keys. Repeater: {0}, Duplicate key: {1}, Duplicate value: {2}",
                  expression, trackById, value);
            } else {
              // new never before seen block
              nextBlockOrder[index] = {id: trackById, scope: undefined, clone: undefined};
              nextBlockMap[trackById] = true;
            }
          }

          // remove leftover items
          for (var blockKey in lastBlockMap) {
            block = lastBlockMap[blockKey];
            elementsToRemove = getBlockNodes(block.clone);
            $animate.leave(elementsToRemove);
            if (elementsToRemove[0].parentNode) {
              // if the element was not removed yet because of pending animation, mark it as deleted
              // so that we can ignore it later
              for (index = 0, length = elementsToRemove.length; index < length; index++) {
                elementsToRemove[index][NG_REMOVED] = true;
              }
            }
            block.scope.$destroy();
          }

          // we are not using forEach for perf reasons (trying to avoid #call)
          for (index = 0; index < collectionLength; index++) {
            key = (collection === collectionKeys) ? index : collectionKeys[index];
            value = collection[key];
            block = nextBlockOrder[index];

            if (block.scope) {
              // if we have already seen this object, then we need to reuse the
              // associated scope/element

              nextNode = previousNode;

              // skip nodes that are already pending removal via leave animation
              do {
                nextNode = nextNode.nextSibling;
              } while (nextNode && nextNode[NG_REMOVED]);

              if (getBlockStart(block) != nextNode) {
                // existing item which got moved
                $animate.move(getBlockNodes(block.clone), null, jqLite(previousNode));
              }
              previousNode = getBlockEnd(block);
              updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, collectionLength);
            } else {
              // new item which we don't know about
              $transclude(function ngRepeatTransclude(clone, scope) {
                block.scope = scope;
                // http://jsperf.com/clone-vs-createcomment
                var endNode = ngRepeatEndComment.cloneNode(false);
                clone[clone.length++] = endNode;

                // TODO(perf): support naked previousNode in `enter` to avoid creation of jqLite wrapper?
                $animate.enter(clone, null, jqLite(previousNode));
                previousNode = endNode;
                // Note: We only need the first/last node of the cloned nodes.
                // However, we need to keep the reference to the jqlite wrapper as it might be changed later
                // by a directive with templateUrl when its template arrives.
                block.clone = clone;
                nextBlockMap[block.id] = block;
                updateScope(block.scope, index, valueIdentifier, value, keyIdentifier, key, collectionLength);
              });
            }
          }
          lastBlockMap = nextBlockMap;
        });
      };
    }
  };
}];