indexOf() please explain it to me.

JavaScript will return -1 if the user calls the indexOf() method on an array and does not find the item searched for (i.e the argument passed into indexOf()), in your example lime is the argument and it is not found in the array so the value of -1 is returned.

If the item is in the array, indexOf() will return the position location of the item searched for. So, if you called items.indexOf('Hat') the method will return 0, which is the location of 'Hat' in items

This is useful, in the event you developed a program that needed to search an array to quickly determine if an email address or some other item was present. If you called the indexOf method and it returned a -1, you could then move on in your program knowing that your search efforts did not result in the item you were searching for...

Abraham, I think you're assuming you already know whether the item you're looking for is in your array. IndexOf tells you where an item is in your array, if it's there. Many times, you already know it's in your array, and you just want to know where to access it. But it's also useful that it lets you know when the item is not in your array at all.

If you're looking for an item in your array, presumably you're going to do something with that item next. Maybe you'll pass that index to another function, or there could be a whole list of things you'd want done with the item. The -1 response tells you that you don't need to do all of those things, because there is no such item. It may save you performance, because you're not wastefully processing things for this nonexistent item, or it may even prevent something from crashing later on.

In the case of a nonexistent item, Javascript couldn't just pass you a number that IS in your array, where you wouldn't know the difference! It could either pass you a number that would never appear as an array index (what they actually did, of course), or it could throw an error that you'd have to catch to avoid crashing. Which would you rather get back?

Thanks guys for clarifying this to me. I appreciate both of your answers.