How to check condition in array JavaScript?

There are some ways to check if elements of the array satisfy a given condition. For example, whether every element is even, or if there is an element that I want to have in the array. Let’s see how to use them in JavaScript.

If you want to make sure every element is fulfilling the condition, it’s perfect to use every() method.

The every() method description

The every() method executes the provided callback function once for each element present in the array until it finds the one where callback returns a falsy value. If such an element is found, the every() method immediately returns false. Otherwise, if the callback returns a truthy value for all elements, the every() method returns true.

Check out the example.

Caution: Calling every() method on an empty array will return true for any condition! Check out the example. So, you need to write additional code to prevent unexpected results.

Check out the example.

If you want to check if one or more elements fulfill the condition, there is some() method.

The some() method description

The some() method executes the callback function once for each element present in the array until it finds the one where callback returns a truthy value. If such an element is found, some() method immediately returns true. Otherwise, if the callback returns a falsy value for all elements, some() method returns false.

Check out the example.

Caution: Calling some() method on an empty array will return false for any condition! So, you need to write additional code to prevent unexpected results.

Check out the example.

You can also use these two methods to check if the array contains what you need. But I don’t recommend using them when you want to only check if the array contains what you need because the code is not only for you. You must write the code with intention.

The every()0 and every()1 methods do exactly what they say. If you used every()0 or every()1 method to check if the array contains what you need, then the programmer who reads this code later might think it’s to find what you need, not to check if the array contains what you need. But in case you still want to use them, I have written down their descriptions with examples below.

The find() method description

The every()0 method executes the callback function once for each index of the array until the callback returns a truthy value. If so, every()0 immediately returns the value of that element. If callback never returns a truthy value (or the array’s length is 0), every()0 method returns undefined.

The findIndex() method description

The every()1 method executes the callback function once for every index in the array until it finds the one where callback returns a truthy value. If such an element is found, every()1 immediately returns the element's index. If callback never returns a truthy value (or the array's length is 0), every()1 method returns -1.

Conclusion

The functions that I explained today are pretty well-known functions, but people don’t know about the return value when the array is empty. So, don’t forget to write additional conditions as I explained above next time. And also, don’t forget to write the code while keeping in mind your intention! It’s very important!

In a programming language like Javascript, to check if the value exists in an array, there are certain methods. To be precise, there are plenty of ways to check if the value we are looking for resides amongst the elements in an array given by the user or is predefined. Let's discuss these methods one by one using various examples.

indexof() method

The indexof() method in Javascript is one of the most convenient ways to find out whether a value exists in an array or not. The indexof() method works on the phenomenon of index numbers. This method returns the index of the array if found and returns -1 otherwise. Let's consider the below code:

Output

The above code prints the given out because the value is already present in the array. It is quite easy to understand that the expected value is present at position 0. Thus, the indexof() method tells you that the value expected is present in the given array.

includes() method

The includes() method is one such method using which we can easily find out whether the expected value exists in the given array. There are various ways to use include() method. This method returns a Boolean value i.e. true if the value exists and false if it incorrect. The includes() method can be used in various ways to find out if the value exists. To name a few, take a look at the below examples to understand.

In the above method, we have defined two variables as shown. The includes() methods return true because the value which we are looking for is already present in the given array. If the value was not present in the array, the includes() methods might have returned false.

Another way of using the includes() method is by assigning the index value through which the element we are looking for is generated as output. See the below code for reference.

In the above code snippet, we have defined the variable "actors" which the value. We have also defined a variable "names" which would return true or false, if the includes() method returns the shown result. The code above will return true since the value and the index number have been correctly assigned and would return the output.

The above examples are some of the predefined methods that we have used to check whether an element exists in the array or not. We have another approach to find out an array element using loops. Let's discuss how can we check if the element exists in an array using loops as shown in the below code snippet.

Using loops

Output

status: Present
status: Absent

In the above code snippet, we have defined an array with some values in the form of strings. We have also defined a function under which the variable status is used as a string to mark if the elements are present in the program. The logical flow of the program is to traverse through each element present in the array and check if the element is present. If the value exists in the array it will display "Present" and "Absent" accordingly.

Summary

Javascript is dynamic and flexible programming as well as a scripting language. It is a powerful developer-friendly natured language that lets you do single stuff in multiple ways so that our learning curve remains steep. In this article, we discussed how we can easily carve different ways through which we can easily find whether the given array consists of the desired value or not. We also came across certain methods and generic programming examples that are not just easy to understand but can be implemented with no absolute knowledge. We have used indexof() and includes() methods in this article since they are the most used methods whenever it is required to find out the value enshrined in an array. We also came across loops through which one can easily find out by the normal linear search traversal as we do in the generic programming paradigms.

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