How to usearray manipulation and join() method in Javascript

Approach 1: Using nested loops

In JavaScript, an array is populated incrementally to form each line of the pattern. The join() method converts the array elements into a string, separating them with spaces. here we are creating a pyramid by using a number pattern.

Example: We are using nested loops, array manipulation, and the join() method, this JavaScript code prints a number pattern with spaces, where numbers increase along each row up to 5.

Javascript

const n = 5;
for (let i = 1; i <= n; i++) {
    let arr = [];
    let count = 1;
    for (let j = 1; j <= 2 * n; ++j) {
        if (i + j >= n + 1 && (i >= j - n + 1)) {
            arr.push(count);
            count++;
        } else {
            arr.push(' ');
        }
    }
    console.log(arr.join(' '));
}

Output

        1          
      1 2 3        
    1 2 3 4 5      
  1 2 3 4 5 6 7    
1 2 3 4 5 6 7 8 9

JavaScript Program to Print Number Pattern

The idea of pattern-based programs is to understand the concept of nesting for loops and how and where to place the alphabet/numbers/stars to make the desired pattern.