Bug in limitTo filter when using negative begin parameter

[scroach]

There is an error in the limitTo filter begin/end position calculations.
I want to show a maximum 5 characters from a string no matter which length it is.

Therefore I am using this snippet: {{string | limitTo : 5 : -5 }}
I expect the filter to show max. 5 chars beginning from the -5 index. This works as long as the string is at least 5 characters long. If it is shorter the filter won't display anything!

Example here:
http://plnkr.co/edit/tSdeeQ1Ue8rxyapC11vV?p=preview

Bug seems to be in any 1.4.x version of angular.

[gkalpak]

Why don't we make limitTo behave like the native slice ?

[scroach]

What do you mean with 'behave like'? Changing the parameters from length/begin to start/end as in slice?

I just looked into the implementation and as the filter internally uses slice anyway there seems to be a bug in the calculation of the end param. When using a negative start parameter for slice end needs to be negative too or omitted. In my example above 5 and -5 result in end to equal 0 and slice returns an empty string.

console.log("123".slice(-3))
> "123"
console.log("123".slice(-3, 0))
> ""

[gkalpak]

@scroach, sorry, it wasn't clear - I meant wrt the begin index.
I.e. right now we have:

begin = (begin < 0 && begin >= -input.length) ? input.length + begin : begin;

whereas slice() worksmore like:

begin = (begin < 0) ? Math.max(0, input.length + begin) : begin;

[gkalpak]

BTW, @scroach, while this is fixed and since limitTo works a little different than slice() (and offers more power in some cases), you can easily return the last X items of an array/string by using a negative limit:

{{ string | limitTo: -5 }}

[scroach]

Ah thx, didn't know that I could also provide a negative limit parameter but thanks for pointing that out and fixing the strange behaviour.