fix: code block

Author: danieldanielecki

data/blog/software-development/web-development/frontend/javascript/slice-vs-substring-vs-substr-complete-javascript-string-methods-comparison.mdx

@@ -788,6 +788,7 @@ console.log("\n=== Example 6: Positive start, negative end (4, -3) ===");
 console.log("slice(4, -3):", str.slice(4, -3));         // "Scr" (from index 4 to -3, which is position 7)
 console.log("substring(4, -3):", str.substring(4, -3)); // "Java" (negative treated as 0, swaps to substring(0, 4))
 console.log("substr(4, -3):", str.substr(4, -3));       // "" (negative length treated as 0)
+```
 
 ## Real-World Use Cases