Javascript: check if an array includes a value (6 ways)

While working in javascript arrays, there is often a requirement to determine if a value exists in an array. This article demonstrates easy ways to check if an array includes a particular value in a javascript using different methods and example illustrations.

Table of Contents:

• Check if a value exists in javascript array using includes()
• Check if a value exists in javascript array using indexOf()
• Check if a value exists in javascript array using iteration
• Check if a value exists in javascript array using some()
• Check if a value exists in javascript array using filter()
• Check if a value exists in javascript array using Set

Check if a value exists in javascript array using includes()

Javascript’s includes() method finds out if a particular value exists in the array or not.

Example:-

Check if the values ‘Popular’ and ‘Hello’ exist in the array [“Javascript”, “Is”, “Popular”,”Language”]

Code:-

function existsInArray(_element,_array)
{
  console.log(_array.includes(_element));
} 
//usage
let myArray = ["Javascript", "Is", "Popular","Language"];
existsInArray("Popular",myArray);
existsInArray("Hello",myArray);

Output:-

true
false

Explanation:-

• In the above code, function existsInArray(_element,_array) is used.
• Within the function, includes() method is used to check if the _element (first argument) exists in the _array (second argument).

Check if a value exists in javascript array using indexOf()

Javascript’s indexOf() method returns the first index of the element if found in the array. If the element is not found then, -1 is returned.

Example:-

Check if the values ‘Popular’ and ‘Hello’ exist in the array [“Javascript”, “Is”, “Popular”,”Language”]

Code:-

function existsInArray(_element,_array)
{
   console.log(_array.indexOf(_element) >=0 );
} 
//usage
let myArray = ["Javascript", "Is", "Popular","Language"];
existsInArray("Popular",myArray);
existsInArray("Hello",myArray);

Output:-

true
false

Explanation:-

• In the above code, function existsInArray(_element,_array) is used.
• Within the function, indexOf() method is used to check if the _element (first argument) exists in the _array (second argument). If the value is not found then _array.indexOf(_element) is less than zero. Else _array.indexOf(_element) is -1.

Check if a value exists in javascript array using iteration

Example:-

Check if the values ‘Popular’ and ‘Hello’ exist in the array [“Javascript”, “Is”, “Popular”,”Language”]

Code:-

function existsInArray(_element,_array)
{
    var length = _array.length;
    for(var i = 0 ; i < length; i++)
    {
        if(_array[i] == _element)
        {
            return true;
        }
    }
    return false;
 } 
//usage
let myArray = ["Javascript", "Is", "Popular","Language"];
console.log(existsInArray("Popular",myArray));
console.log(existsInArray("Hello",myArray));

Output:-

true
false

Explanation:-

• In the above code, function existsInArray(_element,_array) is used.
• Within the function, for loop runs, iterates through all the array elements and compares each element with _element (first argument). If the match is found, true is returned. Else false is returned.

Check if a value exists in javascript array using some()

Javascript’s some() method will test a callback function on all the elements of the calling array and returns true if it finds the element for which the callback function returns true.

Example:-

Check if the values ‘Popular’ and ‘Hello’ exist in the array [“Javascript”, “Is”, “Popular”,”Language”]

Code:-

function existsInArray(_element,_array)
{
    return _array.some(function(element)
    {
        return element == _element;
    }
    )
} 
//usage
let myArray = ["Javascript", "Is", "Popular","Language"];
console.log(existsInArray("Popular",myArray));
console.log(existsInArray("Hello",myArray));

Output:-

true
false

Explanation:-

• In the above code, function existsInArray(_element,_array) is used.
• Here, some() method applies a function on all array elements to find if any element is equal to the value passed in as an argument(_element). If any of the element is found, true is returned. Else, false is returned.

Check if a value exists in javascript array using filter()

Javascript’s filter() method returns a new array that consists of all the elements that pass the test implemented by the function provided.

Example:-

Check if the values ‘Popular’ and ‘Hello’ exist in the array [“Javascript”, “Is”, “Popular”,”Language”]

Code:-

function existsInArray(_element,_array)
{
    return _array.filter(function(e) 
 { return e == _element }).length > 0
 } 
//usage
let myArray = ["Javascript", "Is", "Popular","Language"];
console.log(existsInArray("Popular",myArray));
console.log(existsInArray("Hello",myArray));

Output:-

true
false

Explanation:-

• In the above code, function existsInArray(_element,_array) is used.
• Within the function, filter() is applied, which implements a function on all the array elements and creates a new array with elements that have a value equal to the _element passed in as the first argument.
• Finally, check if the length of the filtered array is greater than zero. If yes, return true, else return false.

Check if a value exists in javascript array using Set

Javascript’s Set enables saving unique values.

Javascript’s Set.prototype.has() method is used to find out if an element with a particular value exists in the SET or not.

Example:-

Check if the values ‘Popular’ and ‘Hello’ exist in the array [“Javascript”, “Is”, “Popular”,”Language”]

Code:-

function existsInArray(_element,_array)
{
    var setOfArrayElements = new Set(_array);
    if (setOfArrayElements.has(_element))
      return true;
    else
      return false;
}
//usage
let myArray = ["Javascript", "Is", "Popular","Language"];
console.log(existsInArray("Popular",myArray));
console.log(existsInArray("Hello",myArray));

Output:-

true
false

Explanation:-

• In the above code, function existsInArray(_element,_array) is used.
• Within the function, all the elements of the array are stored in Set.
• Finally, has() method of Set is used to find if the Set (setOfArrayElements) contains an element with a particular value.

Read More:

• Javascript: Insert an item to array at specific index
• Javascript: Check if an array is empty
• Javascript: Convert array to string (4 ways)

I hope this article helped you to check if a particular value exists in the javascript array. Good Luck !!!