inspect API accept a single node.

src/api.ts

 import peg from 'pegjs';
-import { MfmNode, MfmPlainNode } from './node';
-import { stringifyNode, stringifyTree } from './util';
+import { MfmNode, MfmPlainNode, TEXT } from './node';
+import { stringifyNode, stringifyTree, inspectOne } from './util';
 
 const parser: peg.Parser = require('./parser');
 
@@ -37,13 +37,17 @@ export function toString(node: MfmNode | MfmNode[]): string {
 /**
  * Inspects the MfmNode tree.
 */
-export function inspect(nodes: MfmNode[], action: (node: MfmNode) => void): void {
-	for (const node of nodes) {
-		action(node);
-		if (node.children != null) {
-			inspect(node.children, action);
+export function inspect(node: MfmNode, action: (node: MfmNode) => void): void
+export function inspect(nodes: MfmNode[], action: (node: MfmNode) => void): void
+export function inspect(node: (MfmNode | MfmNode[]), action: (node: MfmNode) => void): void {
+	if (Array.isArray(node)) {
+		for (const n of node) {
+			inspectOne(n, action);
 		}
 	}
+	else {
+		inspectOne(node, action);
+	}
 }
 
 /**

src/util.ts

@@ -147,6 +147,15 @@ export function stringifyTree(nodes: MfmNode[]): string {
 	return dest.map(n => stringifyNode(n)).join('');
 }
 
+export function inspectOne(node: MfmNode, action: (node: MfmNode) => void) {
+	action(node);
+	if (node.children != null) {
+		for (const child of node.children) {
+			inspectOne(child, action);
+		}
+	}
+}
+
 //
 // dynamic consuming
 //

test/api.ts

@@ -32,6 +32,17 @@ after`;
 			});
 			assert.strictEqual(mfm.toString(result), 'hello [tada everynyan!]');
 		});
+
+		it('replace text (one item)', () => {
+			const input = 'good morning [tada everyone!]';
+			const result = mfm.parse(input);
+			mfm.inspect(result[1], node => {
+				if (node.type == 'text') {
+					node.props.text = node.props.text.replace(/one/g, 'nyan');
+				}
+			});
+			assert.strictEqual(mfm.toString(result), 'good morning [tada everynyan!]');
+		});
 	});
 
 	describe('extract', () => {