Function startOperation

mini-code-editor/cm/lib/codemirror.js:1860–1863

()

    // be awkward, slow, and error-prone), but instead updates are
    // batched and then all combined and executed at once.
    function startOperation() {
      updateInput = userSelChange = textChanged = null;
      changes = []; selectionChanged = false; callbacks = [];
    }
    function endOperation() {
      var reScroll = false, updated;
      if (maxLengthChanged) computeMaxLength();