There's a bug in my code

Question

My code isn't working . I'm trying to figure out what the bug is . Can someone help ? ! It's a function that is supposed to return an array of the first n triangular numbers.

For example, listTriangularNumbers(5) returns [1,3,6,10,15].

 function listTriangularNumbers(n) {
 var num;
 var array = [];
 for (i = 1; i <= n; ++i) {
 num = i;
 for (j = i; j >= 1; --j) {
 num = num + j;
 }
 array.push(num);
 }
 return array;
}

• StudioTime: What do you mean it isn't working? What is it doing? What is it NOT doing that you want it to?

Answer 1

Your initial initialization of j is wrong, it's starting at i so it's going too high. Also switched the operators around to make sure the conditions work.

function listTriangularNumbers(n) {
 var num;
 var array = [];
 for (i = 1; i <= n; i++) {
 num = i;
 for (j = i-1; j >= 1; j--) {
 num = num + j;
 }
 array.push(num);
 }
 return array;
}

Answer 2

You can try below code to get help:

a = listTriangularNumbers(8);
console.log(a);
function listTriangularNumbers(n) {
 var num;
 var array = [0];
 for (i = 1; i <= n; i++) {
 num = 0;
 for (j = 1; j <= i; j++) {
 num = num + j;
 }
 array.push(num);
 }
 return array;
}

Answer 3

You actually don't need 2 for-loops to do this operation. A single for-loop would suffice.

function listTriangularNumbers(n) {
 // Initialize result array with first element already inserted
 var result = [1];
 // Starting the loop from i=2, we sum the value of i 
 // with the last inserted element in the array.
 // Then we push the result in the array
 for (i = 2; i <= n; i++) {
 result.push(result[result.length - 1] + i);
 }
 // Return the result
 return result;
}
console.log(listTriangularNumbers(5));

Answer 4

 function listTriangularNumbers(n) {
 var num;
 var array = [];
 for (i = 1; i <= n; ++i) {
 num = i;
 for (j = i-1; j >= 1; --j) {
 num = num + j;
 }
 array.push(num);
 }
 return array;
 }
 var print=listTriangularNumbers(5);
 console.log(print);