JavaScript Program to Print Triangle Star Pattern

0 0 1 minute read

This article will demonstrate how to create a triangle star pattern in JavaScript.

The Possible Triangle Star Patterns are:

Upper left triangle
Upper right triangle
Lower right triangle
Lower left triangle

Approach

To create the triangle start patterns in javascript, we will use a for loop for the n number of iterations, and in each loop we will print the “*” with the repeat method to increase or decrease the number of starts in each iteration. Also to provide proper space create a whitespace string to give the required space before the stars.

Example 1: Upper Left Triangle.

Javascript

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

Output

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

Example 2: Upper Right Triangle.

Javascript

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

Output:

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

Example 3: Lower Right Star Pattern

Javascript

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

Output:

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

Example 4: Lower Left Star Pattern

Javascript

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

Output

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

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