Right-Aligned Alphabet Pyramid in JavaScript

What You’ll Learn

Right-align the pyramid by printing a shrinking number of leading spaces, then printing letters from A up to the current row letter (restarting each row). Because we append letters using String.fromCharCode(k).padStart(2, " "), use a monospace font if you want the right edge to look perfect. Compare Program 22 (right-aligned sequential stream) and Program 16 (centered). Includes a live preview, worked JavaScript examples, edge cases, and complexity.

📝 Problem & Approach

Given a top letter (or fixed E), print a right-aligned pyramid of alphabet prefixes ending at that letter.

// Five rows (monospace; leading spaces + width-2 letters)
//     A
//    A B
//   A B C
//  A B C D
// A B C D E

Inputs & Outputs

Minimal workflow

for i from base to top:
    line = ""
    for j from top down while j > i:
        line += " "
    for k from base to i:
        line += String.fromCharCode(k).padStart(2, " ")
    console.log(line)

Approach comparison

🔮 Live Preview

Choose a top letter from A to F and draw the right-aligned alphabet pyramid in the browser (monospace).

Press "Draw pattern".

Examples Gallery

Three complete JavaScript programs - fixed A–E, user-chosen top letter, and an int-index rewrite. Click View Output to reveal sample console results, or Try it Yourself to run in the browser editor.

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

for (let i = base; i <= top; i++) {
  let line = "";
  for (let j = top; j > i; j--) {
    line += " ";
  }
  for (let k = base; k <= i; k++) {
    line += String.fromCharCode(k).padStart(2, " ");
  }
  console.log(line);
}

    A
   A B
  A B C
 A B C D
A B C D E

let topCh = prompt("Enter top letter (like E):");
topCh = (topCh || "").trim().toUpperCase();
if (topCh.length !== 1 || !/^[A-Z]$/.test(topCh)) {
  console.log("Please enter a single letter.");
} else {
  const base = "A".charCodeAt(0);
  const top = topCh.charCodeAt(0);

  for (let i = base; i <= top; i++) {
    let line = "";
    for (let j = top; j > i; j--) {
      line += " ";
    }
    for (let k = base; k <= i; k++) {
      line += String.fromCharCode(k).padStart(2, " ");
    }
    console.log(line);
  }
}

Enter top letter (like E): C
  A
 A B
A B C

const top = "E".charCodeAt(0);
const base = "A".charCodeAt(0);
const n = top - base + 1;

for (let row = 1; row <= n; row++) {
  let line = "";
  for (let s = 0; s < n - row; s++) {
    line += " ";
  }
  for (let L = 0; L < row; L++) {
    line += String.fromCharCode(base + L).padStart(2, " ");
  }
  console.log(line);
}

    A
   A B
  A B C
 A B C D
A B C D E

🔎 Worked Walkthrough — Top = E

Trace each row’s pad count, letter prefix, and printed line.

Pad count = top - i. Letters always restart at A.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

Each of n rows does O(n) pad + letter work, so total work is O(n²).

💡 Best Practices