export default function applyInlineStyle()

in packages/roosterjs-editor-api/lib/utils/applyInlineStyle.ts [12:69]
50 lines of code
16 McCabe index (conditional complexity)

export default function applyInlineStyle(
    editor: IEditor,
    callback: (element: HTMLElement, isInnerNode?: boolean) => any
) {
    editor.focus();
    let range = editor.getSelectionRange();

    if (range && range.collapsed) {
        let node = range.startContainer;
        let isEmptySpan =
            getTagOfNode(node) == 'SPAN' &&
            (!node.firstChild ||
                (getTagOfNode(node.firstChild) == 'BR' && !node.firstChild.nextSibling));
        if (isEmptySpan) {
            editor.addUndoSnapshot();
            callback(node as HTMLElement);
        } else {
            let isZWSNode =
                node &&
                node.nodeType == NodeType.Text &&
                node.nodeValue == ZERO_WIDTH_SPACE &&
                getTagOfNode(node.parentNode) == 'SPAN';

            if (!isZWSNode) {
                editor.addUndoSnapshot();
                // Create a new text node to hold the selection.
                // Some content is needed to position selection into the span
                // for here, we inject ZWS - zero width space
                node = editor.getDocument().createTextNode(ZERO_WIDTH_SPACE);
                range.insertNode(node);
            }

            applyTextStyle(node, callback);
            editor.select(node, PositionType.End);
        }
    } else {
        // This is start and end node that get the style. The start and end needs to be recorded so that selection
        // can be re-applied post-applying style
        editor.addUndoSnapshot(() => {
            let firstNode: Node;
            let lastNode: Node;
            let contentTraverser = editor.getSelectionTraverser();
            let inlineElement = contentTraverser && contentTraverser.currentInlineElement;
            while (inlineElement) {
                let nextInlineElement = contentTraverser.getNextInlineElement();
                inlineElement.applyStyle((element, isInnerNode) => {
                    callback(element, isInnerNode);
                    firstNode = firstNode || element;
                    lastNode = element;
                });
                inlineElement = nextInlineElement;
            }
            if (firstNode && lastNode) {
                editor.select(firstNode, PositionType.Before, lastNode, PositionType.After);
            }
        }, ChangeSource.Format);
    }
}