Status: New
Owner: ----
New issue 3671 by [email protected]: No short-circuiting done when
calling substr/substring when the same string value would be returned.
https://code.google.com/p/v8/issues/detail?id=3671
See this jsperf page for perf info:
http://jsperf.com/substr-arg-checks
Effectively, V8 appears to do no optimizations if you end up executing code
that turns out to be effectively: someStr.substr(0, someStr.length)
As strings are immutable, it would be a safe optimization to just check for
these values in substr and return the same string without doing any extra
work.
Note 1: runtimes like .Net do this for their immutable strings.
Note 2: I recognize this is a corner case, and is also probably pretty low
pri. However, it would still be nice to have. In our app (the TypeScript
Language Service), this ends up happening a fairly large amount of times.
It was trivial to fix on our side by adding the appropriate check before
doing the .substr call, but it would be very nice if everyone could benefit
from this optimization.
If you guys don't feel that it is worth it, i definitely understand.
Thanks for your consideration!
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