JavaScript Program to Print Pyramid Star Pattern

In this article, we will demonstrate how to create pyramid star patterns in JavaScript.

The Possible Pyramid Star Patterns are:

• Upper pyramid
• Inverted pyramid
• Left inverted pyramid
• Right inverted pyramid

Approach

There will be two different approaches based on alignments i.e. horizontal and vertical.

Horizontally Inverted Pyramid

• This type includes the upper pyramid and the inverted pyramid.
• To achieve this we will use a javascript for loop to iterate N time
• In that loop, print spaces repeat N-1 times before and after the start.
• As the number of start changes by 2 in every line repeat the stars 2*i -1 times to get the required structure.

Vertically Inverted Pyramid

• Vertically inverted pyramids include the Rigth inverted and Left inverted pyramids
• To achieve this we will use Javascript for loop 2 time i.e. from 1 to N and back to 1.
• In that loop, print spaces repeat N-i times before and after the start.
• As the number of start changes by 1 in every line repeat the stars i times to get the required structure.

Example 1: Upper pyramid

Javascript

let n = 5;
for (let i = 1; i <= n; i++) {
    let str = "* ";
    let space = '  ';
    console.log(space.repeat((n - i)) + str.repeat(i * 2 - 1));
}

Output

        * 
      * * * 
    * * * * * 
  * * * * * * * 
* * * * * * * * * 

Example 2: Inverted pyramid

Javascript

let n = 5;
for (let i = n; i >= 1; i--) {
    let str = "* ";
    let space = '  ';
    console.log(space.repeat((n - i)) + str.repeat(i * 2 - 1));
}

Output

* * * * * * * * * 
  * * * * * * * 
    * * * * * 
      * * * 
        * 

Example 3: Left inverted pyramid

Javascript

let n = 5;
for (let i = 1; i <= n; i++) {
    let str = "* ";
    let space = '  ';
    console.log(space.repeat((n - i)) + str.repeat(i));
}

for (let i = n - 1; i >= 1; i--) {
    let str = "* ";
    let space = '  ';
    console.log(space.repeat(n - i) + str.repeat(i));
}

Output

        * 
      * * 
    * * * 
  * * * * 
* * * * * 
  * * * * 
    * * * 
      * * 
        * 

Example 4: Right inverted pyramid

Javascript

let n = 5;
for (let i = 1; i <= n; i++) {
    let str = "* ";
    console.log(str.repeat(i));
}
for (let i = n - 1; i >= 1; i--) {
    let str = "* ";
    console.log(str.repeat(i));
}

Output

* 
* * 
* * * 
* * * * 
* * * * * 
* * * * 
* * * 
* * 
*