Use string interpolation

src/mfm/html-to-mfm.ts

@@ -45,7 +45,7 @@ export default function(html: string): string {
 
 					if (part.length == 2) {
 						//#region ホスト名部分が省略されているので復元する
-						const acct = txt + '@' + (new URL(href.value)).hostname;
+						const acct = `${txt}@${(new URL(href.value)).hostname}`;
 						text += acct;
 						break;
 						//#endregion

src/mfm/html.ts

@@ -44,8 +44,8 @@ const handlers: { [key: string]: (window: any, token: any, mentionedRemoteUsers:
 
 	hashtag({ document }, { hashtag }) {
 		const a = document.createElement('a');
-		a.href = config.url + '/tags/' + hashtag;
-		a.textContent = '#' + hashtag;
+		a.href = `${config.url}/tags/${hashtag}`;
+		a.textContent = `#${hashtag}`;
 		a.setAttribute('rel', 'tag');
 		document.body.appendChild(a);
 	},