Javascript parseInt with number from parseFloat( > 1 million) not working

I already had put a PR 3 years ago that apparently just got totally ignored, but there is a problem with parsing float and integers with high numbers (more than 1 million).
My use case is simple.

Users enter a textfield with a float number representing seconds, that can go more than 1000.
this number need to be converted to milliseconds integers inside a javascript script.
I get my number of milliseconds, floating with var msFloat = parseFloat(input)*1000
and then I get a rounded number without decimals with parseInt(msFloat).

The problem is that there is a problem in the chain where msFloat gets converted to scientific notation, and parseInt is not liking it.

What would be the good way to work on that ?
Thank you