 # JavaScript: Check whether a given matrix is lower triangular or not

## JavaScript Basic: Exercise-121 with Solution

Write a JavaScript program to check whether a given matrix is lower triangular or not.

Note: A square matrix is called lower triangular if all the entries above the main diagonal are zero.

Sample Solution:

HTML Code:

``````<!DOCTYPE html>
<html>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title> Check whether a given matrix is lower triangular or not</title>
<body>

</body>
</html>
```
```

JavaScript Code:

``````function lower_triangular_matrix(user_matrix) {
for (var i = 0; i < user_matrix.length; i++)
{
for (var j = 0; j < user_matrix.length; j++)
{
if (j > i && user_matrix[i][j] !== 0)
return false;
}
}
return true;
}

console.log(lower_triangular_matrix([[1, 0, 0],[2, 0, 0], [0, 3, 3]]));
console.log(lower_triangular_matrix([[1, 0, 1],[2, 0, 0], [0, 3, 3]]));
``````

Sample Output:

```true
false
```

Flowchart: ES6 Version:

``````function lower_triangular_matrix(user_matrix) {
for (let i = 0; i < user_matrix.length; i++)
{
for (let j = 0; j < user_matrix.length; j++)
{
if (j > i && user_matrix[i][j] !== 0)
return false;
}
}
return true;
}

console.log(lower_triangular_matrix([[1, 0, 0],[2, 0, 0], [0, 3, 3]]));
console.log(lower_triangular_matrix([[1, 0, 1],[2, 0, 0], [0, 3, 3]]));
``````

Live Demo:

See the Pen javascript-basic-exercise-121 by w3resource (@w3resource) on CodePen.

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﻿

## JavaScript: Tips of the Day

Returns the sum of the powers of all the numbers from start to end (both inclusive)

Example:

```const sumPower = (end, power = 2, start = 1) =>
Array(end + 1 - start)
.fill(0)
.map((x, i) => (i + start) ** power)
.reduce((a, b) => a + b, 0);
console.log(sumPower(10)); // 385
console.log(sumPower(10, 3)); // 3025
console.log(sumPower(10, 3, 5)); // 2925
```

Output:

```385
3025
2925
```