#    
#  Overview
The `firstIndex(of:)` method is used to return the first index of a specified array element.
#  
#  Syntax
```swift
arr.firstIndex(of: element)
```
#  
## Parameters
**`element`**: The element to search for in the array or collection.

## 
## Return value
This method returns the first index where the element is found. If the element is not found, `nil` is returned.
## 
## Example

// create arrays
let evenNumbers = [2, 4, 6, 8, 10]
let twoLetterWords = ["up", "go", "me", "we"] 
let names = ["John", "James", "Theodore"]

// get index of some elements
let result1 = evenNumbers.firstIndex(of : 4)!
let result2 = twoLetterWords.firstIndex(of: "go")!
let result3 = names.firstIndex(of: "Theodore")!

// print results
print(result1)
print(result2)
print(result3)

#  
## Explanation
* Lines 2 and 3: We create some arrays.
* Lines 7 to 9: We get the index of the elements specified using the `firstIndex(of:)` method. And we store the results in some variables.
* Lines 12 to 14: We print our results.

What is array.firstIndex(of:) in Swift?

Returns the first index of a specified element in an array or nil if not found.