How to Check If a Value Exists in an Array – JavaScript?

  The indexOf() method returns the index of the element inside the array if it is found, and returns -1 if it not found.

  This method is used to  check whether a given value or element exists in an array or not,like this:

<script>
  var fruits = ["Apple", "Banana", "Mango", "Orange", "Papaya"];
  // Check if a value exists in the fruits array
  if(fruits.indexOf("Mango") !== -1)
{
    alert("Value exists!")
  } else
{
    alert("Value does not exists!")
  }
</script>

  ES6 has introduced the includes() method to perform this task very easily. But, this method returns only true or false instead of index number,

For ex:

<script>
  var fruits = ["Apple", "Banana", "Mango", "Orange", "Papaya"];
  alert(fruits.includes("Banana")); // Outputs: true
  alert(fruits.includes("Coconut")); // Outputs: false
  alert(fruits.includes("Orange")); // Outputs: true
  alert(fruits.includes("Cherry")); // Outputs: false
</script>