The findIndex Method In JS

The findIndex Method In JS: Hello everyone, welcome to the nkcoderz.com website. In this article we will going to discuss about the The findIndex Method In JS.

The findIndex method in JavaScript is a method of the Array object that returns the index of the first element in an array that satisfies a provided testing function. If no elements pass the test, it returns -1.

The findIndex Method In JS

Here’s the syntax for using the findIndex method:

array.findIndex(callback(element[, index[, array]])[, thisArg])

where:

• callback: A function to be run for each element in the array, taking three arguments: element, index, and array. The element is the current element being processed in the array. The index is the index of the current element, and the array is the array findIndex was called upon. The callback function should return true if the element is the one you are looking for, and false otherwise.
• thisArg (optional): Object to use as this when executing callback.

Here’s an example that demonstrates how to use the findIndex method to find the index of an element in an array:

Code 1 For findIndex Method

const numbers = [5, 10, 15, 20, 25, 30];
const index = numbers.findIndex(number => number === 20);
console.log(index);

Output

3

In this example, the findIndex method is used to find the index of the element with a value of 20 in the numbers array. The result is logged to the console and it returns 3, which is the index of the element with a value of 20 in the array.

The findIndex method can be useful in many situations where you need to find the index of a specific element in an array. Here are a few more examples to illustrate its use:

Code 2 For findIndex Method

const fruits = ['apple', 'banana', 'cherry', 'strawberry'];

const index = fruits.findIndex(fruit => fruit === 'cherry');
console.log(index);

const users = [
  {id: 1, name: 'John'},
  {id: 2, name: 'Jane'},
  {id: 3, name: 'Jim'}
];

const userIndex = users.findIndex(user => user.id === 2);
console.log(userIndex);

Output

2

1

In the first example, the findIndex method is used to find the index of the element with the value of ‘cherry’ in the fruits array. In the second example, the findIndex method is used to find the index of the user with an id of 2 in the users array.

It’s worth noting that the findIndex method only returns the index of the first element that satisfies the provided testing function. If there are multiple elements in the array that meet the criteria, only the index of the first one will be returned.

If you need to find all indices of elements that meet the criteria, you could use the filter method in combination with the map method to achieve this:

Code 3 For findIndex Method

const allIndices = fruits.reduce((indices, fruit, index) => {
  if (fruit === 'cherry') {
    indices.push(index);
  }
  return indices;
}, []);
console.log(allIndices);

Output

[2]

Conclusion

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