I want to make a reverse triangle using 'for' loop, which should look like this:

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

This what I got:

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

And this is my code:

function rightTriangle(n) {
  for (var i = 0; i <= n; i++) {
    for (var j = n - 1; j >= i; j--) {
      document.write('*');
    }
    document.write('<br>');
  }
}
rightTriangle(5);

I want to make a reverse triangle using 'for' loop, which should look like this:

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

This what I got:

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

And this is my code:

function rightTriangle(n) {
  for (var i = 0; i <= n; i++) {
    for (var j = n - 1; j >= i; j--) {
      document.write('*');
    }
    document.write('<br>');
  }
}
rightTriangle(5);

Please help me out with this task, I would be so appreciated!

• javascript
• algorithm
• for-loop

5 Answers 5

Add the below code to leave the intendation

for(var k=0; k<i; k++){
    document.write("&nbsp;");
}

function rightTriangle (n) {
    for (var i = 0; i <= n; i++) {
        for(var k=0; k<i; k++){
          document.write("&nbsp;");
        }
        for (var j = n-1; j >= i; j--) {
            document.write('*');
        }
        document.write('<br>');
    }
}
rightTriangle(5);

html{
  font-family:monospace;
}

function rightTriangle(n) {
  for (var i = 0; i <= n; i++) {
    for (var j = 0; j <= n; j++) {
      if(j>=i) document.write('*');
      else document.write('&nbsp&nbsp');
    }
    document.write('<br>');
  }
}
rightTriangle(5);

Algo

• Create n*n matrix with 2 values, " " and "*"
• In html " " has no effect as extra spaces are trimmed. You will have to use  , unicode value for single space.
• Now loop and add necessary parts to string.
• Since you need reverse triangle, spaces will e first. You can loop in ascending fashion with value of i denoting spaces and n-i denoting "*"

function rightTriangle(n) {
  var html = "";
  for (var i = 0; i < n; i++) {
    for(var j = 0; j< i; j++){
      html += "&nbsp;";
    }
    for(var k = 0; k< n-i; k++){
      html += "*"
    }
    html +="<br/>"
  }
  document.querySelector('.content').innerHTML = html
}
rightTriangle(5);

.content {
  font-family: monospace;
}

<div class="content"></div>

string.repeat

function rightTriangle(n) {
  var html = "";
  for (var i = 0; i < n; i++) {
    html += "&nbsp;".repeat(i) + "*".repeat(n - i) + "</br>"
  }
  document.querySelector('.content').innerHTML = html
}
rightTriangle(5);

.content {
  font-family: monospace;
}

<div class="content"></div>

Also note that using document.write and < br/>" are considered bad practice.

Here is the most simple solution:

 const prompt = require("prompt-sync")();

 let n = parseInt(prompt("Enter the number of rows: "));

 let string = "";
 function printPyramid(row) {
    for (let i = 0; i < n; i++) {
    string += " ".repeat(i) + "*".repeat(n - i);
    string += "\n";
  }
 }
 printPyramid(n);
 process.stdout.write(string);

1. This code must work on ur terminal or any online js piler.

// 3 for loops are used here; i for rows, j for spaces , k for printing stars

function invertedRightTri(n){
    var str="";
    for(i=1;i<=n;i++){       
        for(j=n-i;j<n;j++){
            str+=" ";
        }
        for (k=0;k<n-i+1;k++){
            str+="*";
        }
        str+="\n";
    }
    return str;
}
var ans=invertedRightTri(5);
console.log(ans);