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HTML Search Methods

Posted by chelseacheevers
chelseacheevers
13,786 Points

LastIndexOf

I am struggling to understand the concept of LastIndexOf()... I have searched other examples and remain mystified. Here are some from MDN:

let anyString = 'Brave new world';

console.log('The index of the first w from the beginning is ' + anyString.indexOf('w'));
// logs 8
console.log('The index of the first w from the end is ' + anyString.lastIndexOf('w'));
// logs 10

I would have thought the index of the first w from the end would have been 6! And 10 would have been the 'e' in Brave.

I know I am missing something, any insight would be appreciated!

1 Answer

Michael Cook
Michael Cook
2,125 Points
Michael Cook
Michael Cook
2,125 Points

The String.lastIndexOf(char) method finds the index of the last occurrence of the character you pass to it. String.indexOf(char) finds the first occurrence of the character you pass it. Both these string methods look at the string from left to right, the same way you would read it. Also, the indices of a string work the exact same way as an array - they start at 0 and every character (including spaces) has an index.

So, if you count each character in your string from left to right, you'll see that 8 and 10 make perfect sense.

Don't be afraid to read the MDN docs. I know they can be a bit challenging, but the more you read them the more they will make sense. Hope this answer helps you.

chelseacheevers
chelseacheevers
13,786 Points

Oh wow! Yes that fully cleared it up thank you! I was definitely misunderstanding. Thanks again!!