**`Array.findIndex()`** is a method in JavaScript that returns the index of a first array element that satisfies the provided condition; otherwise, if no such element exists, it returns -1. This method was first introduced to JavaScript with ES6. 

Note that ``Array.findIndex()`` does not execute the function for array elements without values, nor does it change the original array.

# Syntax

array.findIndex(function(valueToBeFound, index, arr), thisValue)

- valueToBeFound - required value, it represents the value we want to find in the array
- index - optional value, represents the array index of the current element
- arr - optional value, represents the array object the current element belongs to
- thisValue - optional value to be passed to the function to be used as its "this" value. If this parameter is empty, the value "undefined" will be passed as its "this" value

# Examples

const cities = ["Paris", "Barcelona", "New York", "Moscow"]

function getCity(city) {
  return city === "New York";
}

console.log(cities.findIndex(getCity)) // 2


const lunch = ["Pizza", "Lasagna", "Pumpkin Pie", "Steak"]

function getFood(meal) {
  return meal === "Spaghetti";
}

console.log(lunch.findIndex(getFood)) // returns index -1 since Spaghetti is not found in the lunch array


## `Array.findIndex()` using arrow function

By using the arrow function introduced with ES6, the syntax of this method can be simplified even further, as shown in the following example:


const videoGames = ["Dragon Age: Inquisition", "Mass Effect 3", "Greedfall", "The Witcher 3"];

const index = videoGames.findIndex(game => game === "Mass Effect 3");

console.log(index); // 1
console.log(videoGames[index]); // "Mass Effect 3"


Array.findIndex() in ES6

Array.findIndex() returns the index of the first element that meets a condition, or -1 if none.

Array.findIndex() in ES6

Syntax

Examples

Array.findIndex() using arrow function

`Array.findIndex()` using arrow function