In this font-size resizing tutorial:
the author uses parseFloat with a second argument, which I read here:
Is supposed to specify the base of the supplied number-as-string, so that you can feed it '0x10' and have it recognized as HEX by putting 16 as the second argument.
The thing is, no browser I've tested seems to do this.
Are these guys getting confused with Java?
No, they're getting confused with parseInt(), which can take a radix parameter. parseFloat(), on the other hand, only accepts decimals. It might just be for consistency, as you should always pass a radix parameter to parseInt() because it can treat numbers like 010 as octal, giving 8 rather than the correct 10.
来源：https://stackoverflow.com/questions/8555649/second-argument-to-parsefloat-in-javascript