Add this keyword for variables in the same file

src/_data/sitemeta.js

@@ -1,13 +1,13 @@
 module.exports = {
 	siteName: "Leilukin's Hub",
 	siteUrl: "https://leilukin.neocities.org" || "http://localhost:8080",
-	feedUrl: siteUrl + "/feed.xml",
+	feedUrl: this.siteUrl + "/feed.xml",
 	siteLocale: "en_MY",
 	siteLanguage: "en",
 	siteDescription: "Leilukin's personal website.",
 	siteAuthor: {
 		name: "Leilukin",
 		email: "leilukin@outlook.com",
-		url: "https://leilukin.neocities.org/about"
+		url: this.siteUrl + "/about"
 	}
 }