umd/fieldstack.js
/**
   * When a collapsed cursor is at the start of the first styled block, or
   * an empty styled block, changes block to 'unstyled'. Returns null if
   * block or selection does not meet that criteria.
   */
When a collapsed cursor is at the start of the first styled block, or
an empty styled block, changes block to 'unstyled'. Returns null if
block or selection does not meet that criteria.
When a collapsed cursor is at the start of the first styled block or an empty styled block changes block to ' unstyled ' . Returns null if block or selection does not meet that criteria .
function tryToRemoveBlockStyle(editorState) {
    var selection = editorState.getSelection();
    var offset = selection.getAnchorOffset();
    if (selection.isCollapsed() && offset === 0) {
      var key = selection.getAnchorKey();
      var content = editorState.getCurrentContent();
      var block = content.getBlockForKey(key);
      var firstBlock = content.getFirstBlock();
      if (block.getLength() > 0 && block !== firstBlock) {
        return null;
      }
      var type = block.getType();
      var blockBefore = content.getBlockBefore(key);
      if (type === 'code-block' && blockBefore && blockBefore.getType() === 'code-block' && blockBefore.getLength() !== 0) {
        return null;
      }
      if (type !== 'unstyled') {
        return DraftModifier_1.setBlockType(content, selection, 'unstyled');
      }
    }
    return null;
  }
function tryToRemoveBlockStyle ( editorState ) { var selection = editorState . getSelection ( ) ; var offset = selection . getAnchorOffset ( ) ; if ( selection . isCollapsed ( ) && offset === 0 ) { var key = selection . getAnchorKey ( ) ; var content = editorState . getCurrentContent ( ) ; var block = content . getBlockForKey ( key ) ; var firstBlock = content . getFirstBlock ( ) ; if ( block . getLength ( ) > 0 && block !== firstBlock ) { return null ; } var type = block . getType ( ) ; var blockBefore = content . getBlockBefore ( key ) ; if ( type === 'code-block' && blockBefore && blockBefore . getType ( ) === 'code-block' && blockBefore . getLength ( ) !== 0 ) { return null ; } if ( type !== 'unstyled' ) { return DraftModifier_1 . setBlockType ( content , selection , 'unstyled' ) ; } } return null ; }
When a collapsed cursor is at the start of the first styled block, or
 an empty styled block, changes block to 'unstyled'.
When a collapsed cursor is at the start of the first styled block or an empty styled block changes block to ' unstyled ' .