How to Get/Find First Index of Element in Array JavaScript

If you want to find or get an element’s first position or index in an array. You can use the findindex() function; In this tutorial, we will show you how to find or get the first occurrence element position or index in a JavaScript array using the js array method.

How to Get or Find First Index of Element in Array JavaScript

The FindIndex method helps you to get the first index or position of occurrence element in the array that satisfies the given specific test condition.

The basic Syntax of the findIndex() method

The following syntax demonstration of the findIndex() method:

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

Parameters

The findIndex() takes two parameters:

• The first one is the callback function and it’s optional.
• The second one is used as this inside the callback.

1) callback

The callback is a function to execute on each element of the array. It accepts 3 parameters:

• element is the current element of an array.
• index the index of the current element of an array.
• array the array that the findIndex() was called upon.

2) thisArg

The thisArg parameter is an optional object to be used this when executing the callback. If you omit the thisArg argument, the findIndex() function uses undefined.

Return value

For each element of an array, The findIndex() executes the callback function until the callback returns a truthy value.  In this case, the findIndex() immediately returns the value of that element. Otherwise, it returns undefined.

Note that, JS findIndex() method is truly different from the find() method, The find() method is used to search the first element in an array.

Examples of Get/Find Index of First Element in Array JavaScript

First, you have an array with some items. Let’s say it’s an array of numbers.

const numbers = [1, 2, 3, 4, 5];

Now you want to find the position of first odd number from array. You can use findIndex function like following:

let numbers = [1, 2, 3, 4, 5];
console.log(numbers.findIndex(e => e % 2 == 1));

Output:

0

If you want to find first even number index or position in an array, you can do it by using the following:

let numbers = [1, 2, 3, 4, 5];
console.log(numbers.findIndex(e => e % 2 == 0));

Output:

1

Suppose that you have a list of computers objects with name and price properties as follows:

let computers = [{
    name: 'Dell',
    price: 60000
}, {
    name: 'HP',
    price: 50000
}, {
    name: 'Apple',
    price: 80000
}];

The following javascript code uses the findIndex() method to find the first computer position in an array, whose price is greater than $ 60000.

let computers = [{
    name: 'Dell',
    price: 60000
}, {
    name: 'HP',
    price: 50000
}, {
    name: 'Apple',
    price: 80000
}];
console.log(computers.findIndex(c => c.price > 60000));

Output:

2

Conclusion

That’s it; you have learned how to use the JavaScript Array’s findIndex() method to get or find the first occurrence element position or index in an array.

Recommended JavaScript Tutorials