JavaScript Alphabet Pattern Programs

Beginner

6 min read

Updated: Nov 2026

3 examples

fromCharCode

Definition

Definition and Usage

A JavaScript alphabet pattern is a console program that prints letters in rows. The outer for loop chooses the row. The inner for loop appends each letter with line +=, then console.log(line) ends that row.

JavaScript has no char type. "A" is a string, so "A" + col concatenates ("A1", "A2"). Add the codes instead: String.fromCharCode("A".charCodeAt(0) + col) walks A, B, C. Keep the offset inside 0–25 when the shape should stay in A–Z.

Build the row, then log it.

line += letter stays on the same string. console.log(line) runs once after the inner loop and starts the next row.

Syntax

JavaScript Syntax

The same three pieces show up in every program below: a row loop, a code, and console.log.

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



for (let row = 1; row <= 5; row++) {

  let line = "";

  for (let col = 0; col < row; col++)

    line += String.fromCharCode(start + col);  // same row

  console.log(line);                            // end the row

}

Reference

How JavaScript Prints a Letter

Map each part of the console shape to a JavaScript value or call.

Piece	JavaScript	What it does
Letter code	`"A".charCodeAt(0)`	Number 65, the code for A
Next letter	`String.fromCharCode(code)`	Turns that number back into a one-character string
Jump	`fromCharCode(start + col)`	Column 0 is A, column 1 is B
Same line	`line += letter`	No newline between letters
New row	`console.log(line)`	Write the row and finish it
Indent	`" ".repeat(n)`	Leading spaces for pyramids
A–Z slice	`letters.slice(0, n)`	Same growing row without a code loop

Code

JavaScript Examples

Three programs. Each one changes only the JavaScript that picks the letter or the space.

Example 1 — Grow a row with `fromCharCode`

Restart at "A".charCodeAt(0) on every row, then add the column.

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



for (let row = 1; row <= 5; row++) {

  let line = "";

  for (let col = 0; col < row; col++) {

    line += String.fromCharCode(start + col);

  }

  console.log(line);

}

How It Works

The outer for sets how many letters this row prints.
start + col is a number; fromCharCode turns it into a letter.
console.log(line) writes the finished string and ends the row.

Example 2 — Add the column to the code, not the string

"A" + col is string concatenation. The letter comes from the numeric code.

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

const rows = 4;



for (let row = 0; row < rows; row++) {

  let line = "";

  for (let col = 0; col <= row; col++) {

    line += String.fromCharCode(start + col);

  }

  console.log(line);

}

How It Works

"A" + 1 is the string "A1", not the letter B.
charCodeAt(0) + col is a number, and fromCharCode maps it back to a letter.
Column 0 is A, column 1 is B, and so on.

Example 3 — Indent with `" ".repeat`

Put spaces on the string before the letters so the triangle sits on the right.

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

const rows = 4;



for (let row = 1; row <= rows; row++) {

  let line = " ".repeat(rows - row);

  for (let col = 0; col < row; col++) {

    line += String.fromCharCode(start + col);

  }

  console.log(line);

}

How It Works

" ".repeat(rows - row) builds the leading spaces in one call.
The inner loop appends letters with the same fromCharCode sum.
Fewer spaces and more letters on each later row pull the shape right.

Programs

34 JavaScript Alphabet Pattern Programs

Each card is a full JavaScript program: nested for loops, charCodeAt and fromCharCode, and the letters console.log writes. Open one for the walkthrough.

Alphabet Pattern 1

Sample output

  A
  AB
  ABC
  ABCD
  ABCDE

Alphabet Pattern 2

Sample output

  E
  ED
  EDC
  EDCB
  EDCBA

Alphabet Pattern 3

Sample output

  E
  DE
  CDE
  BCDE
  ABCDE

Alphabet Pattern 4

Sample output

  A
  BA
  CBA
  DCBA
  EDCBA

Alphabet Pattern 5

Sample output

  ABCDE
  ABCD
  ABC
  AB
  A

Alphabet Pattern 6

Sample output

  ABCDE
  BCDE
  CDE
  DE
  E

Alphabet Pattern 7

Sample output

  EDCBA
  DCBA
  CBA
  BA
  A

Alphabet Pattern 8

Sample output

  EDCBA
  EDCB
  EDC
  ED
  E

Alphabet Pattern 9

Sample output

  A
  BB
  CCC
  DDDD
  EEEEE

Alphabet Pattern 10

Sample output

  E
  DD
  CCC
  BBBB
  AAAAA

Alphabet Pattern 11

Sample output

  EEEEE
  DDDD
  CCC
  BB
  A

Alphabet Pattern 12

Sample output

  AAAAA
  BBBB
  CCC
  DD
  E

Alphabet Pattern 13

Sample output

  A
  B C
  D E F
  G H I J
  K L M N O

Alphabet Pattern 14

Sample output

  A
  ABC
  ABCDE
  ABCDEFG
  ABCDEFGHI

Alphabet Pattern 15

Sample output

  ABCDEEDCBA
  ABCD**DCBA
  ABC****CBA
  AB******BA
  A********A

Alphabet Pattern 16

Sample output

    A
  B C D
E F G H I

Alphabet Pattern 17

Sample output

  EDCB*
  EDC*A
  ED*BA
  E*CBA
  *DCBA

Alphabet Pattern 18

Sample output

  A
  ABA
  ABCBA
  ABCDCBA
  ABCDEDCBA

Alphabet Pattern 19

Sample output

  A        A
  AB      BA  
  ABC    CBA
  ABCD  DCBA
  ABCDEEDCBA

Alphabet Pattern 20

Sample output

    A
   BA
  CBA
 DCBA
EDCBA

Alphabet Pattern 21

Sample output

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

Alphabet Pattern 22

Sample output

        A
      B C
    D E F
  G H I J
K L M N O

Alphabet Pattern 23

Sample output

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

Alphabet Pattern 24

Sample output

A
BAB
CBABC
DCBABCD
EDCBABCDE

Alphabet Pattern 25

Sample output

A B C D E
F G H I
J K L
M N
O

Alphabet Pattern 26

Sample output

ABCDE
BCDEA
CDEBA
DECBA
EDCBA

Alphabet Pattern 27

Sample output

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

Alphabet Pattern 28

Sample output

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

Alphabet Pattern 29

Sample output

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

Alphabet Pattern 30

Sample output

ABCDE
BABCD
CBABC
DCBAB
EDCBA

Alphabet Pattern 31

Sample output

A       A
 B     B
  C   C
   D D
    E

Alphabet Pattern 32

Sample output

    A
   ABA
  ABCBA
 ABCDCBA
ABCDEDCBA

Alphabet Pattern 33

Sample output

    A
   B B
  C   C
 D     D
E       E

Alphabet Pattern 34

Sample output

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

Frequently Asked Questions

Why does "A" + col print A1 instead of B?

JavaScript has no char type. "A" is a string, so "A" + 1 concatenates and becomes "A1". Add the codes instead: String.fromCharCode("A".charCodeAt(0) + col) is the letter.

What is the difference between line += and console.log?

line += letter appends to the same string, which is how each letter in a row is placed. console.log(line) writes that string and ends the row. Call it once after the inner loop.

What happens if the row count is greater than 26?

fromCharCode continues past Z into other characters. For A–Z demos, keep rows between 1 and 26. Number(input) returns NaN for a bad token; check Number.isInteger before you use the count.

Can I print the same shape with slice instead of a code loop?

Yes. Store "ABCDEFGHIJKLMNOPQRSTUVWXYZ" and call slice(0, length) for a row that always starts at A. Nested fromCharCode loops are the skill these programs teach; slice is a shortcut once the shape is clear.

Next: Alphabet Pattern 1

A full JavaScript walkthrough of the right-angled letter triangle, from "A".charCodeAt(0) through console.log.

Alphabet Pattern 1 →

About the author

Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

Experience 12 years building web and cloud systems
Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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JavaScript Number Pattern Programs JavaScript Alphabet Pattern 1

JavaScript Alphabet Pattern Programs

Definition and Usage

JavaScript Syntax

How JavaScript Prints a Letter

JavaScript Examples

Example 1 — Grow a row with fromCharCode

How It Works

Example 2 — Add the column to the code, not the string

How It Works

Example 3 — Indent with " ".repeat

How It Works

34 JavaScript Alphabet Pattern Programs

Frequently Asked Questions

Related JavaScript Topics

Alphabet Pattern 1

Number Patterns

Star Patterns

JavaScript Strings

Next: Alphabet Pattern 1

About the author

Example 1 — Grow a row with `fromCharCode`

Example 3 — Indent with `" ".repeat`