# JavaScript: Search JavaScript arrays with a binary search

## JavaScript Function: Exercise-18 with Solution

Write a function for searching JavaScript arrays with a binary search.

Note : A binary search searches by splitting an array into smaller and smaller chunks until it finds the desired value.

Pictorial Presentation:

Sample Solution: -

HTML Code:

``````<!DOCTYPE html>
<html>
<meta charset=utf-8 />
<title>Search JavaScript arrays with a binary search</title>
<body>

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

JavaScript Code:

``````function array_binarySearch(narray, delement) {
var mposition = Math.floor(narray.length / 2);

if (narray[mposition] === delement){
return mposition;
}
else if (narray.length === 1)
{
return null;
}
else if (narray[mposition] < delement) {
var arr = narray.slice(mposition + 1);
var res = array_binarySearch(arr, delement);
if (res === null)
{
return null;
}
else {
return mposition + 1 + res;
}
}
else {
var arr1 = narray.slice(0, mposition);
return array_binarySearch(arr1, delement);
}
}

var myArray = [1, 2, 3, 5, 6, 7, 10, 11, 14, 15, 17, 19, 20, 22, 23];
console.log(array_binarySearch(myArray, 6));
```
```

Sample Output:

```4
```

Flowchart:

Live Demo:

See the Pen JavaScript - Search JavaScript arrays with a binary search-function-ex- 18 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