Array indexOf()

Its syntax:


indexOf(itemToLookFor, optionalIndexToStartWith)

indexOf() starts searching from the front of the array. indexOf() returns the position of the item in the array or -1 if the item isn't in the array.

An identity comparison is used during comparing.

 
<!DOCTYPE html>
<html>
<head>
    <title>Example</title>
    <script type="text/javascript">
        var numbers = [1,2,3,4,5,4,3,2,1]; 
        document.writeln(numbers.indexOf(4)); //3 
        document.writeln(numbers.indexOf(4, 4)); //5 
        
        var person = { name: "JavaScript" }; 
        var people = [{ name: "JavaScript" }]; 
        
        var morePeople = [person]; 
        document.writeln(people.indexOf(person)); //-1 
       
    </script>
</head>
<body>
</body>
</html>
Click to view the demo
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    Essential Types  

Array:
  1. The Array Type
  2. Array Built-in Methods
  3. Detecting Arrays
  4. Get and set array values
  5. Enumerating the Contents of an Array
  6. Array Length
  7. Array join() method
  8. Array concat()
  9. Array indexOf()
  10. Array lastIndexOf()
  11. Array every()
  12. Array filter() filters array with the given function.
  13. Array map()
  14. Array forEach()
  15. push() and pop():Array Stack Methods
  16. push(), shift():Array Queue Methods
  17. Array reduce()
  18. Array reduceRight()
  19. reverse():Reordering array
  20. Array slice()
  21. Array some()
  22. Array splice()
  23. Array sort()
  24. toString(), toLocaleString() and valueOf Array
  25. Array unshift()