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JavaScript JavaScript Loops, Arrays and Objects Tracking Multiple Items with Arrays Useful Array Methods

Peter May
Peter May
16,376 Points

Why does the if statement "instock.indexOf(search) < -1" not work unless I change it to ">=0".

I couldn't get the search function to find stuff until I changed the if statement from ">-1" to ">=0". why doesn't it wrok with "-1"?

if(inStock.indexOf( search ) >=0 ){ print('yes we have '+ search+ ' in our stock.</p>'); } else{ print(search + ' is not in stock.');

Here is a link to my code.


2 Answers

Steven Parker
Steven Parker
218,861 Points

You've mentioned a few different comparison operations, only one would work.

  • if your test is " > -1", it should work
  • but " >= -1" would not work because it accepts the not-found condition (-1)
  • also " < -1" would not work because it is looking for other negative values

indexOf returns -1 if the element is not exists in the array. if the evultion of the expression returns a number above -1 it means that the element is inside the array- it give u back the index.