Rotating Number Pattern in JavaScript

What You’ll Learn

The rotating number pattern prints 12345, then 23451, then 34521, … — each row starts at i and wraps back to 1 — a natural follow-up after Program 38’s decreasing-width triangle. This tutorial covers forward and wrap-around inner loops, row rotation, nested loops, a live preview, worked JavaScript examples, edge cases, and complexity.

📝 Problem & Approach

Given max_num = 5, print a rotating number pattern: for each row i, print ascending i..max_num then wrap with i-1..1.

// max_num = 5
// 12345
// 23451
// 34521
// 45321
// 54321

Inputs & Outputs

Minimal workflow

for i from 1 to max_num:
    for j from i to max_num: print j
    for k from i-1 down to 1: print k
    print newline

Approach comparison

🔮 Live Preview

Choose a row count between 3 and 9 and draw the rotating number pattern in the browser.

Press "Draw pattern".

Examples Gallery

Three complete JavaScript programs — fixed width, prompt() input, and a smaller trace demo. Click View Output to reveal sample console results, or Try it Yourself to run the code live.

const max_num = 5;

for (let i = 1; i <= max_num; i++) {
  let line = "";
  for (let j = i; j <= max_num; j++) {
    line += j;
  }
  for (let k = i - 1; k >= 1; k--) {
    line += k;
  }
  console.log(line);
}

12345
23451
34521
45321
54321

const maxInput = prompt("Enter the maximum number:");
const max_num = parseInt(maxInput, 10);

if (!Number.isFinite(max_num) || max_num < 1) {
  console.log("Please enter a positive integer.");
} else {
  for (let i = 1; i <= max_num; i++) {
    let line = "";
    for (let j = i; j <= max_num; j++) {
      line += j;
    }
    for (let k = i - 1; k >= 1; k--) {
      line += k;
    }
    console.log(line);
  }
}

Enter the maximum number: 3
123
231
321

const max_num = 3;

for (let i = 1; i <= max_num; i++) {
  let line = "";
  for (let j = i; j <= max_num; j++) {
    line += j;
  }
  for (let k = i - 1; k >= 1; k--) {
    line += k;
  }
  console.log(line);
}

123
231
321

🔎 Worked Walkthrough — max_num = 5

Trace each outer-loop value of i, forward and wrap segments, and full row output.

Each row prints exactly max_num digits — total digits = n × n = n².

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices