Increasing Jump Number Triangle Pattern in JavaScript

What You’ll Learn

The increasing jump number triangle starts each row at i and jumps forward with a decreasing step m — a natural step after the continuous counter in Program 20. This tutorial covers the shape rule, step logic, a live preview, algorithm steps, worked JavaScript examples, edge cases, and complexity.

📝 Problem & Approach

Given a positive integer rows, print an increasing jump number triangle: row i starts with i, then prints i - 1 more values computed by adding a decreasing step m.

// rows = 5 (conceptual shape)
// 1
// 2 6
// 3 7 10
// 4 8 11 13
// 5 9 12 14 15
for (let i = 1; i <= rows; i++) {
  let line = i + " ";
  let m = rows - 1;
  let k = i + m;
  for (let j = 1; j < i; j++) {
    line += k + " ";
    m--;
    k = k + m;
  }
  console.log(line);
}

Inputs & Outputs

Minimal workflow

for i from 1 to rows:
    line = i + " "
    m = rows - 1
    k = i + m
    for j from 1 to i - 1:
        append k + " " to line
        m = m - 1
        k = k + m
    console.log(line)

Approach comparison

🔮 Live Preview

Choose a row count between 1 and 15 and draw the jump number triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete JavaScript programs — fixed row count, user input, and custom initial step for m. Click View Output to reveal sample results, or Try it Yourself to run the code live.

const rows = 5;

for (let i = 1; i <= rows; i++) {
  let line = i + " ";
  let m = 4;
  let k = i + m;

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

1 
2 6 
3 7 10 
4 8 11 13 
5 9 12 14 15

const rowsInput = prompt("Enter the number of rows:");
const rows = parseInt(rowsInput, 10);

for (let i = 1; i <= rows; i++) {
  let line = i + " ";
  let m = rows - 1;
  let k = i + m;

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

Enter the number of rows: 4
1 
2 5 
3 6 8 
4 7 9 10

const rows = 4;

for (let i = 1; i <= rows; i++) {
  let line = i + " ";
  let m = 3;
  let k = i + m;

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

1 
2 5 
3 6 8 
4 7 9 10

🔎 Worked Walkthrough — rows = 5

Trace each outer-loop value of i, the initial m, and the numbers printed on each row.

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

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices