Reverse Alphabet Triangle in JavaScript

What You’ll Learn

The reverse alphabet triangle grows each row by one letter, but every row counts down to A instead of up from it. This tutorial covers the shape rule, descending inner loop, a live preview, algorithm steps, worked JavaScript examples, edge cases, and complexity.

📝 Problem & Approach

Given a positive integer rows, print a left-aligned reverse alphabet triangle where row i starts at the i-th letter and counts down to A.

// First 5 rows (conceptual shape)
// A
// BA
// CBA
// DCBA
// EDCBA

Inputs & Outputs

Minimal workflow

for i from 0 to rows - 1:
    for code from (A + i) down to A:
        print letter (no newline)
    print newline

Approach comparison

🔮 Live Preview

Choose a row count between 1 and 26 and draw the reverse alphabet triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete JavaScript programs — fixed row count, prompt input, and a slice-reverse shortcut. Click View Output to reveal sample console results, or Try it Yourself to run in the browser editor.

const rows = 5;
const base = "A".charCodeAt(0);

for (let i = 0; i < rows; i++) {
  let line = "";
  for (let code = base + i; code >= base; code--) {
    line += String.fromCharCode(code);
  }
  console.log(line);
}

A
BA
CBA
DCBA
EDCBA

const rowsInput = prompt("Enter the number of rows (max 26):");
let rows = parseInt(rowsInput, 10);
rows = Math.max(1, Math.min(rows, 26));

const base = "A".charCodeAt(0);

for (let i = 0; i < rows; i++) {
  let line = "";
  for (let code = base + i; code >= base; code--) {
    line += String.fromCharCode(code);
  }
  console.log(line);
}

Enter the number of rows (max 26): 4
A
BA
CBA
DCBA

const rows = 5;
const clampedRows = Math.max(1, Math.min(rows, 26));
const letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

for (let i = 0; i < clampedRows; i++) {
  console.log(letters.slice(0, i + 1).split("").reverse().join(""));
}

A
BA
CBA
DCBA
EDCBA

🔎 Worked Walkthrough — rows = 5

Trace each outer-loop index and see what the descending inner loop prints down to A.

Total letter prints: 1 + 2 + 3 + 4 + 5 = 15 = 5×6/2.

🎯 Practice Problems

Try these variations to lock in the reverse pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices