JavaScript Program to Print Diamond Shape Star Pattern

This article will demonstrate how to create the diamond start pattern in JavaScript.

Possible Diamond Start Patterns:

• Solid Diamond Start Pattern
• Hollow Diamond Star Pattern
• Inverted Hollow Diamond Pattern

Approach to Create Diamond Star Pattern:

• The approach to creating a diamond star pattern will use 2 JavaScript Nested For loops to print the upper and lower half of the diamond.
• We will iterate from 1 to N and back to 1 to cover the diamond structure for input N.
• The nested loop will be used to create the string that contains the row to be printed each time with the condition of diamond that row+column > N and N+row < column.
• Print the resultant string each time using the console.log() method that adds a new line at the end of the output the form the required structure.

Example 1: Solid Diamond Start Pattern

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

Output

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

Example 2: Hollow Diamond Star Pattern

Javascript

let n = 5;
for (let i = 1; i <= n; i++) {
    let str = ''

    for (let j = 1; j <= 2 * n; ++j) {
        if (i + j == n + 1 || (i == j - n + 1)) {
            str += '*'
        }
        else
            str += ' '
    }

    console.log(str);
}
for (let i = n - 1; i >= 1; i--) {
    let str = ''
    for (let j = 1; j <= 2 * n; ++j) {
        if (i + j == n + 1 || (i == j - n + 1))
            str += '*'
        else
            str += ' '
    }

    console.log(str);
}

Output

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

Example 3: Inverted Hollow Diamond Pattern

Javascript

let n = 5;
for (let i = 1; i <= n; i++) {
    let str = ''
    for (let j = 1; j < 2 * n; ++j) {
        if (i + j > n + 1 && (i > j - n + 1))
            str += ' ';
        else
            str += '*';
    }

    console.log(str);
}
for (let i = n - 1; i >= 1; i--) {
    let str = ''
    for (let j = 1; j < 2 * n; ++j) {
        if (i + j > n + 1 && (i > j - n + 1))
            str += ' ';
        else
            str += '*';
    }

    console.log(str);
}

Output

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