Lately I've been writing very processor heavy Javascript. I feel like it could
benefit a lot from having a syntax feature for removing debug statements.
Obviously JS is interpreted and not compiled, so I'm not sure if this sounds
completely unrealistic, but it has some very useful scenarios.
I like to write verbose type checking for functions to check ranges and throw
exceptions if invalid input is detected. The issue is in a production
environment (especially with games) the code executes too slowly with all the
extra branches. It would be nice if there was a simple syntax to treat code as
if it's commented out when a flag is set. In some languages this is done with
preprocessor statements like:
#if debug
console.log("Debug Mode");
#else
console.log("Release Mode");
#endif
The alternative is simply:
const debug = false;
if (debug)
{
// Tons of type checking
}
What I'd expect would be possible for an implementer is to get to the constant
and evaluate the branch and remove the whole statement before running it
through the JIT. This would allow a very standard way to turn on and off pieces
of code. An example program:
// Debug Off Control
{
console.time("benchmark control");
for (var i = 0; i < 10000000; ++i)
{
}
console.timeEnd("benchmark control");
}
// Debug Off
{
const debugOff = false;
var debugOffCounter = 0;
console.time("benchmark debug off");
for (var i = 0; i < 10000000; ++i)
{
if (debugOff)
{
debugOffCounter++;
}
}
console.timeEnd("benchmark debug off");
}
// Debug On
{
const debugOn = true;
var debugOnCounter = 0;
console.time("benchmark debug on");
for (var i = 0; i < 10000000; ++i)
{
if (debugOn)
{
debugOnCounter++;
}
}
console.timeEnd("benchmark debug on");
}
http://jsfiddle.net/9LCra/
On the latest Firefox there's a 11 ms difference between the control and using
a constant in the if. In chrome there's a 23 ms difference. Is there anything
stopping an implementer from evaluating the constant and making the control and
debug off identical in performance?
I kind of want this to be like a standard goto technique that's expected to
work since I believe right now the alternative is to simply create two files or
remove anything that might slow things down.
I decided to post here first in case there's a fundamental reason that such a
use case would be impossible or if an alternative was in the works that would
fit this goal.
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