Toggle Underline Template for Templater

/**
 * Templater Template for Obsidian - Text Underlining Toggle
 *
 * This template provides a toggle functionality for underlining selected text in Obsidian notes.
 * It handles the following operations:
 * 1. If text is not underlined: Adds HTML underlining tags and converts newlines to <br> tags
 * 2. If text is already underlined: Removes underlining and converts <br> tags back to newlines
 *
 * Usage:
 * 1. Select text in your Obsidian note
 * 2. Trigger this template
 * 3. The text will toggle between underlined and non-underlined states
 */

<%*
// Get the currently selected text from the editor
const text = tp.file.selection();

/**
 * Checks if the text already has HTML underlining tags
 * @param {string} text - The text to check
 * @returns {boolean} - True if text has underlining tags, false otherwise
 */
const hasUnderlineTags = text => {
    return text.startsWith('<u>') && text.endsWith('</u>');
};

/**
 * Converts newlines to HTML break tags
 * @param {string} text - The text to process
 * @returns {string} - Text with newlines replaced by <br> tags
 */
const addBreakTags = text => {
    return text.replace(/\n/g, '<br>');
};

/**
 * Converts HTML break tags back to newlines
 * @param {string} text - The text to process
 * @returns {string} - Text with <br> tags replaced by newlines
 */
const removeBreakTags = text => {
    return text.replace(/<br>/g, '\n');
};

let result;
if (hasUnderlineTags(text)) {
    // If text is already underlined, remove the formatting
    result = text
        .replace('<u>', '')        // Remove opening underline tag
        .replace('</u>', '')       // Remove closing underline tag
        .replace(/<br>/g, '\n');   // Convert break tags back to newlines
} else {
    // If text is not underlined, add the formatting
    result = `<u>${addBreakTags(text)}</u>`;
}

// Return the processed text to replace the selection
tR += result;
%>