# JavaScript: Returns n rows by n columns identity matrix

## JavaScript Function: Exercise-10 with Solution

Write a JavaScript function which returns the n rows by n columns identity matrix.

Pictorial Presentation:

Sample Solution: -

HTML Code:

``````<!DOCTYPE html>
<html>
<meta charset=utf-8 />
<title>Returns the n rows by n columns identity matrix</title>
<body>

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

JavaScript Code:

``````function matrix(n) {

var i;
var j;

for (i=0; i < n; i++)
{
for (j=0; j < n; j++)
{
if (i === j)
{

console.log(' 1 ');
}

else
{
console.log(' 0 ');}
}
console.log('----------');
}
}
matrix(4);
```
```

Sample Output:

``` 1
0
0
0
----------
0
1
0
0
----------
0
0
1
0
----------
0
0
0
1
----------
```

Flowchart:

Live Demo:

See the Pen JavaScript -Returns n rows by n columns identity matrix-function-ex- 10 by w3resource (@w3resource) on CodePen.

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## JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

```const string = "foo";
const substring = "oo";

console.log(string.includes(substring));
```

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:

```var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);
```

Ref: https://bit.ly/3fFFgZv