value - 0 is an idiom to apply ToNumber in JS. (+ 0 is not typically used because "string" + 0 => "string0").
I've run octane and found box2d performs this several times.
(The code `... - 0` can be seen in kraken's fft, dft, etc. But this path is not used in the benchmark run).
Of course, before doing this, we should investigate the impact more...