1let n = 5; // you can take input from prompt or change the value
2let string = "";
3// External loop
4for (let i = 1; i <= n; i++) {
5  // printing spaces
6  for (let j = 1; j <= n - i; j++) {
7    string += " ";
8  }
9  // printing star
10  for (let k = 0; k < 2 * i - 1; k++) {
11    string += "*";
12  }
13  string += "\n";
14}
15console.log(string);

1let n = 5;
2let string = "";
3for (let i = 1; i <= n; i++) {
4  for (let j = 0; j < i; j++) {
5    string += "*";
6  }
7  string += "\n";
8}
9console.log(string);