Using Math.trunc instead of Math.floor suggests that the argument could be negative.

[samreid]

During code review #103, we observed 4 occurrences of Math.trunc, which MDN describes like so:

The Math.trunc() static method returns the integer part of a number by removing any fractional digits.
[...]
Unlike the other three Math methods: Math.floor(), Math.ceil() and Math.round(), the way Math.trunc() works is very simple. It truncates (cuts off) the dot and the digits to the right of it, no matter whether the argument is a positive or negative number.

In the cases we reviewed, it seems like the argument should be non-negative, and we recommend using Math.floor so readers don't misconstrue the argument as possibly negative.

[pixelzoom]

Converted to Math.floor after fuzz testing with assert && assert( Math.trunc( value ) === Math.floor( value ) ) at usage sites.