Plaintext fix

js/markdown.js

 	 * @returns {string} concatenated HTML
 	 */
 	_childHTML(state) {
-		return this.children.map((child) => child.toHTML(state)).join('');
+		return MDNode.toHTML(this.children, state);
+	}
+
+	/**
+	 * Protected helper that renders and concatenates the plaintext of all
+	 * children of this node.
+	 *
+	 * @param {MDState} state
+	 * @returns {string} concatenated plaintext
+	 */
+	_childPlaintext(state) {
+		return MDNode.toPlaintext(this.children, state);
 	}
 
 	/**
 		for (const symbol of symbolOrder) {
 			let content = footnotes[symbol];
 			if (!content) continue;
-			text += `${symbol}. ${content.toPlaintext(state)}\n`;
+			text += `${symbol}. ${this._childPlaintext(state)}\n`;
 		}
 		return text.trim();
 	}
  */
 class Markdown {
 	/**
-	 * Set of standard readers.
+	 * Set of standard readers to handle common syntax.
 	 * @type {MDReader[]}
 	 */
 	static standardReaders = [
 	];
 
 	/**
-	 * All supported readers.
+	 * All supported readers except `MDLineBreakReader`.
 	 * @type {MDReader[]}
 	 */
 	static allReaders = [
 
 	/**
 	 * Keeps removing first and last lines of markdown to locate the source of
-	 * an exception.
+	 * an exception and prints the minimal snippet to `console.error`.
 	 *
 	 * @param {string[]} lines
 	 * @param {string} elementIdPrefix

markdownjs.html

 		<script src="js/markdown.js"></script>
 		<script src="js/spreadsheet.js"></script>
 		<script>
-			var activeReaders = [];
-			var parser = null;
-			function onDocumentLoad() {
-				activeReaders = Markdown.standardReaders.slice();
-				parser = new Markdown(activeReaders);
-				document.getElementById('markdowninput').addEventListener('input', onMarkdownChange);
-				populateReaderCheckboxes();
-				setTimeout(onMarkdownChange, 0);
-			}
-			function onMarkdownChange() {
-				let markdown = document.getElementById('markdowninput').value;
-				let html = parser.toHTML(markdown, 'foo-');
-				document.getElementById('preview').innerHTML = html;
-			}
 			var blockReaderClasses = {
 				'Heading (underline)': MDUnderlinedHeadingReader,
 				'Heading (hash)': MDHashHeadingReader,
 				'Modifiers': MDModifierReader,
 				'Line breaks': MDLineBreakReader,
 			};
+			var activeReaders = [];
+			var parser = null;
+			function onDocumentLoad() {
+				activeReaders = [ ...Markdown.allReaders, new MDSpreadsheetReader() ];
+				parser = new Markdown(activeReaders);
+				document.getElementById('markdowninput').addEventListener('input', onMarkdownChange);
+				populateReaderCheckboxes();
+				setTimeout(onMarkdownChange, 0);
+			}
+			function onMarkdownChange() {
+				const textarea = document.getElementById('markdowninput');
+				let markdown = textarea.value;
+				let html = parser.toHTML(markdown, 'foo-');
+				document.getElementById('preview').innerHTML = html;
+			}
 			function populateReaderCheckboxes() {
 				const container = document.getElementById('readercontainer');
 				var header = document.createElement('div');