Top 10 JavaScript Array Methods Every Web Developer Must Know

In JavaScript, arrays are influential and powerful in helping web developers and designers do almost everything. However, when it comes to implementing JavaScript for web development or app development, there are specific 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 discussing top JavaScript array methods, let's begin with a brief introduction to arrays. 

What is an array in JavaScript?

An array is a data structure in JavaScript that stores various 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 individually. 

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

Understanding how to manipulate and manage data efficiently is crucial for robust application development when working with JavaScript arrays. Additionally, developers often encounter scenarios where they must handle dates and times within these arrays, such as chronologically sorting events or calculating durations. Many comprehensive guides explore practical techniques and tips to understand JavaScript date and time manipulation.

Array Declaration in JavaScript

An array can be declared in two ways. Here is an example to understand both 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 are built-in functions that can be implemented into the arrays to perform specific calculations or make changes. JavaScript Developers can save time by writing routine tasks 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. It performs a callback function on each component one by one until it finds the ones that return the actual value. Those elements will show as 'true'. It will return 'false' for the rest of the array elements. 

This method returns the actual value based on three arguments. These arguments are value, index, and the object that is being transversed.

If 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 added to the array once the technique 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 helps reduce the array to a single value. In JavaScript app development as well as web development, the 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. 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 checks all the elements for the defined function. It will then test all the elements to find whether they all pass the test for a specific value. If the test is passed, it will return a true. Otherwise, it will return a false.

For example, if an array includes the ages of all the teachers in the school, 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 when it finds a 'false' value and returns a 'false' value.

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:e index, array object, and currentValue. 

Here is the syntax for the map( ) method:

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

  // return element for newArray, after executing something

}[, thisArg]);

5. flat( )

Implementing the flat( ) method will form a new array using the sub-array elements linked together in a series, following a rule until 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 empty slots in an array, then this method can be applied to eliminate 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 Java 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 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

7. forEach()

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

Several things must be considered 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 change the array on which the function is executed. 

Following is the syntax for forEach( ) method:

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

  // execute something

8. findIndex( )

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

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

Here is the syntax for the findIndex( ) method:

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

9. sort( )

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

By default, the sorting of elements is done in ascending order. The function can be executed for the elements' numerical and alphabetical values. 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'. The specified value will return a 'false' if it is not found.

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

arr.includes(valueToFind[, fromIndex])

Handing over to you:

If you are a developer, the methods mentioned above will be instrumental. These are the most popular methods every developer should know 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 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 cosy place.