Top 10 JavaScript Array Methods Every Web Developer Must Know

In JavaScript, the arrays play an influential and powerful role to help web developers and designers do almost everything. However, when it comes to implementing JavaScript for web development or app development, there are certain array methods that every developer should be aware of. Learning and using these array methods will help them to bring out their true potential.

 

Before diving into the discussion about top JavaScript array methods, let’s begin with a brief introduction of arrays. 

 

What is an array in JavaScript?

 

An array is actually a data structure in JavaScript that stores various types of elements or values in it. The elements in the array are stored as a single variable so that the developers can access those elements through a single channel, without going through the entire list one by one. 

 

In web development services, one of the main reasons behind using JavaScript is that arrays here don’t refer to multiple variables. In most of the other languages, the arrays store elements in different variables, which makes things a bit difficult for developers, especially in cross platform app development. 

 

Array Declaration in JavaScript

 

An array can be declared in two ways. Here is an example to understand both the ways:

 

var House = [ ]; // way 1
var House = new array(); // way 2

 

Top Array Methods in JavaScript

 

To unleash the full potential of JavaScript, it is crucial to use the array methods. These methods come as built-in functions that can be implemented to the arrays to perform specific calculations or make changes. JavaScript Developers can save their important time by writing the routine functions from scratch. 

 

Let’s jump to the best JavaScript array methods that every developer must be using today:

 

1. some( )

 

To carry out a callback function for all the elements in an array, the some( ) method can work effectively. What it does is perform a callback function on each element one by one until it finds the ones that return true value. For those elements, it will show ‘true’. For the rest of the array elements, it will return ‘false’. 

 

This method returns the true value on the basis of three arguments. These arguments are: value, index, and the object that is being transversed.

 

In case the developers deliver a ‘this argument (thisArg)’ parameter to some( ) method, then this method will use the parameter as ‘this’ value of the callback. In other cases, the ‘this’ value will depend on the undefined values and the regular rules that find the ‘this’ in a function.

 

It should be noted that the some( ) method does not visit the elements that are added to the array once the method has been carried out already. Moreover, it also doesn’t check the deleted elements. 

 

Here is how a some( ) method is carried out: 

 

arr.some(callback(element[, index[, array]])[, thisArg])

 

2. reduce()

 

This array method is useful in reducing the array to a single value. In JavaScript app development as well as web development, reduce( ) array method is used by developers to execute a function that applies to all the elements in the array (from left to right).

 

The accumulator saves the return value of the function. It should be noted that if any array elements don’t have a value, the function will not be executed to those elements. Also, the values of the existing array will not change. The syntax for reduce( ) is:

 

arr.reduce(callback( accumulator, currentValue[, index[, array]] )[, initialValue])

 

3. every( )

 

The every( ) array method is used to check all the elements for the defined function. It will then run a test of all the elements to find whether all of them pass the test for a certain value. If the test is passed, it will return a true. Otherwise, it will return a false.

 

For example, if an array includes ages of all the teachers in the school and the function is to check whether all of them are below 30. Then the

every( ) method will check all the array elements. If all of them are under 30, it will show a ‘true’. It will stop the process the time it finds a ‘false’ value, and return a ‘false’.

 

Syntax for every( ) method is:

 

arr.every(callback(element[, index[, array]])[, thisArg])

 

4. map( )

 

When developers want to form a new array with the outcomes of the callback function on all the elements in the array, the map( ) method can be used. 

 

Here, the callback function will get three arguments, which are index, array object, and currentValue. 

 

Here is the syntax for map( ) method:

 

let newArray = arr.map(callback(currentValue[, index[, array]]) {

  // return element for newArray, after executing something

}[, thisArg]);

 

5. flat( )

 

Implementation of the flat( ) method will form a new array using the sub-array elements linked together in a series, following a rule till the specified depth. 

 

The role of the depth parameter here is to define how deep the array structure will get flatted. The default number of levels to flat the elements is 1. 

If there are some empty slots in an array, then this method can be applied to get rid of the empty holes. Syntax for flat( ) array method is:

 

var newArray = arr.flat([depth]);

 

6. filter( )

 

As the name suggests, the filter( ) method is used to apply filters to an array and then create a new array with the returned elements. In a web design and development services, when the filter( ) is executed, it tests all the array elements for the applied function. The elements that pass the test form a new array.

 

For example, this method can be applied to find the prime numbers in an array and then create a new array containing the results. 

 

The filter( ) method doesn’t test the elements that have been deleted before executing the function. The elements that don’t pass the test are simply skipped and are not added to the new array. Following is the syntax for this array method:

 

let newArray = arr.filter(callback(currentValue[, index[, array]]) {

  // return element for newArray, if true

}[, thisArg]);

 

7. forEach()

 

This array method is applied to apply a function to each element present in the array. The function works in ascending order. 

 

A number of things are needed to be taken care of while using the forEach( ) method. First, the developers can’t stop or break the loop once the function has been executed, apart from applying some exceptions. Second, it doesn’t make any changes to the array on which the function is executed. 

 

Following is the syntax for forEach( ) method:

 

arr.forEach(callback(currentValue[, index[, array]]) {

  // execute something

}[, thisArg]);

 

8. findIndex( )

 

The findIndex( ) method is used to find the index for executed function in the array. When a function is executed, it tests all the elements once, until it finds the one for which the function is executed. It will then return ‘true’. 

 

If the desired index is not found in any element or no element passes the test, then it will return -1. 

 

Here is the syntax for findIndex( ) method:

 

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

 

9. sort( )

 

The sort( ) array method does exactly what its name says. It is a common method in JavaScript that developers should use to sort the array elements. Once all the elements are sorted, it will return the new array. 

 

By default, the sorting of elements is done in ascending order. The function can be executed for both numerical and alphabetical values of the elements. The syntax for the sort( ) method looks like this:

 

arr.sort([compareFunction])

 

10. includes( )

 

To determine if an array contains a specific value among the elements, the developers can use the includes( ) function. If the array string includes the specified value, it will return a ‘true’. If the specified value is not found, it will return a ‘false’.

 

It is worth noting that the characters for includes( ) method are case sensitive. While comparing, it checks whether the character is in capital letter or small letter. Below is the syntax for the includes( ) method:

 

arr.includes(valueToFind[, fromIndex])

 

Handing over to you:

 

If you are a developer, the use of array methods mentioned above will prove to be very useful for you. These are the most popular methods that every developer should be aware of today.

 

The aim of using these functions and methods is to make the development efforts simple. These methods can save time and amplify code performance.

 

Author Bio: 

 

Keith Laurance is a technical content writer who has been working with the cross-platform app development team at Octal IT Solutions. Over the years she has researched JavaScript app development and promises to deliver the most reliable solutions. Other than researching tech-related queries, she loves to eat and read books. You can always find her in the nearby market buying quirky elements for her super cozy place.