VirtualRepeatController.prototype.virtualRepeatUpdate_ = function()

in src/components/virtualRepeat/virtual-repeater.js [755:856]

• 84 lines of code
• 21 McCabe index (conditional complexity)

VirtualRepeatController.prototype.virtualRepeatUpdate_ = function(items, oldItems) {
  this.isVirtualRepeatUpdating_ = true;

  var itemsLength = items && items.length || 0;
  var lengthChanged = false;

  // If the number of items shrank, keep the scroll position.
  if (this.items && itemsLength < this.items.length && this.container.getScrollOffset() !== 0) {
    this.items = items;
    var previousScrollOffset = this.container.getScrollOffset();
    this.container.resetScroll();
    this.container.scrollTo(previousScrollOffset);
  }

  if (itemsLength !== this.itemsLength) {
    lengthChanged = true;
    this.itemsLength = itemsLength;
  }

  this.items = items;
  if (items !== oldItems || lengthChanged) {
    this.updateIndexes_();
  }

  this.parentNode = this.$element[0].parentNode;

  if (lengthChanged) {
    this.container.setScrollSize(itemsLength * this.itemSize);
  }

  // Detach and pool any blocks that are no longer in the viewport.
  Object.keys(this.blocks).forEach(function(blockIndex) {
    var index = parseInt(blockIndex, 10);
    if (index < this.newStartIndex || index >= this.newEndIndex) {
      this.poolBlock_(index);
    }
  }, this);

  // Add needed blocks.
  // For performance reasons, temporarily block browser url checks as we digest
  // the restored block scopes ($$checkUrlChange reads window.location to
  // check for changes and trigger route change, etc, which we don't need when
  // trying to scroll at 60fps).
  this.$browser.$$checkUrlChange = angular.noop;

  var i, block,
      newStartBlocks = [],
      newEndBlocks = [];

  // Collect blocks at the top.
  for (i = this.newStartIndex; i < this.newEndIndex && this.blocks[i] == null; i++) {
    block = this.getBlock_(i);
    this.updateBlock_(block, i);
    newStartBlocks.push(block);
  }

  // Update blocks that are already rendered.
  for (; this.blocks[i] != null; i++) {
    this.updateBlock_(this.blocks[i], i);
  }
  var maxIndex = i - 1;

  // Collect blocks at the end.
  for (; i < this.newEndIndex; i++) {
    block = this.getBlock_(i);
    this.updateBlock_(block, i);
    newEndBlocks.push(block);
  }

  // Attach collected blocks to the document.
  if (newStartBlocks.length) {
    this.parentNode.insertBefore(
        this.domFragmentFromBlocks_(newStartBlocks),
        this.$element[0].nextSibling);
  }
  if (newEndBlocks.length) {
    this.parentNode.insertBefore(
        this.domFragmentFromBlocks_(newEndBlocks),
        this.blocks[maxIndex] && this.blocks[maxIndex].element[0].nextSibling);
  }

  // Restore $$checkUrlChange.
  this.$browser.$$checkUrlChange = this.browserCheckUrlChange;

  this.startIndex = this.newStartIndex;
  this.endIndex = this.newEndIndex;

  if (this.isFirstRender) {
    this.isFirstRender = false;
    var firstRenderStartIndex = this.$attrs.mdStartIndex ?
      this.$scope.$eval(this.$attrs.mdStartIndex) :
      this.container.topIndex;

    // The first call to virtualRepeatUpdate_ may not be when the virtual repeater is ready.
    // Introduce a slight delay so that the update happens when it is actually ready.
    this.$mdUtil.nextTick(function() {
      this.container.scrollToIndex(firstRenderStartIndex);
    }.bind(this));
  }

  this.isVirtualRepeatUpdating_ = false;
};