To find the first index of an array in javascript; In this tutorial, you will learn JavaScript findIndex()
method and how to search/get/find the first occurrence element index or position in an array using this javascript array method.
How to find index of an element position in an array in javaScript tutorial will take several examples for demonstration of how to find first index occurrence position in the array.
JavaScript Array findIndex()
method
You can use the new method findIndex()
to find first occurrence position of an array. Because in es6 enhance the capability to finding the first position of an element in the javascript array.
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 thecallback
.
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 thefindIndex()
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: JavaScript findIndex()
Suppose you have a numeric array and want to search the first odd number position in it, you can use these findIndex()
method for these.
See the following example:
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 find 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
In this tutorial, you have learned how to use the JavaScript Array’s findIndex()
method and using this method how to find the first occurrence Index or position in an array.
Beautiful work you are doing here. Keep it up!