JavaScript lastIndexOf() | Get Last Index of an Element

The JavaScript lastIndexOf() method returns the last index of specified element in a specified array. For example:

HTML with JavaScript Code

<!DOCTYPE html>
<html>
<body>

   <p id="xyz"></p>

   <script>
      const cities = ["Tokyo", "Los Angeles", "Bangkok", "Dubai", "Los Angeles", "Berlin"];
      let x = cities.lastIndexOf("Los Angeles");
      document.getElementById("xyz").innerHTML = x;
   </script>
   
</body>
</html>

Output

In above example, the following JavaScript statement:

let x = cities.lastIndexOf("Los Angeles");

states that the index number of last Los Angeles from the array named cities will initialize to a variable named x.

Note - Indexing always starts with 0. Therefore Tokyo is at index number 0. Similarly the first Los Angeles is at index number 1, and the last Los Angeles is at index number 4.

JavaScript lastIndexOf() Syntax

The syntax of lastIndexOf() method in JavaScript is:

array.lastIndexOf(item, start)

Note - The item parameter is required and is used to specify the value that has to be searched in array.

Note - The start parameter is optional and is used to specify, from where to start the search. The default value of this parameter is the index of last element, that is array.length-1.

Note - The lastIndexOf() method returns -1, in case if the specified value does not exists in the given array.

JavaScript lastIndexOf() Example

HTML with JavaScript Code

<!DOCTYPE html>
<html>
<body>

   <p id="abc"></p>

   <script>
      const myarray = ["Tokyo", "Bangkok", "Tokyo", "Dubai", "Berlin", "Tokyo", "Frankfurt"];
      let lio = myarray.lastIndexOf("Tokyo", 3);
      document.getElementById("abc").innerHTML = lio;
   </script>
   
</body>
</html>

Output

If I remove 3 (the value of start parameter), then the output should be 5. Because the last Tokyo is at index number 5. But since I specified 3 from where to start the search. Therefore, the last Tokyo before index number 3, is available at index number 2.

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