Added support for floats. See related issue.

[jvonmitchell]

Now floats will pad.

[jvonmitchell]

This is a better pull request.

[Daiz]

Adding lodash as a dependency for a module as small and simple as this feels pretty silly, especially when it could be replaced with a simple for or while loop. It's more bloat than efficiency. And speaking of efficiency, the math approach is pretty illegible and slow - a simple regex approach using /(\d+)(\.\d+)/works much faster based on quick testing (see this jsperf).

With all that said, I'm not even sure if I'd want zpad to pad floats like this all the time - the basic idea of padding is to get strings of equal length, and decimals could easily wreck that. With that in mind, I'm considering adding an extra parameter float, where you could define padding for decimals. The idea is that you could then do this:

var zpad = require('zpad').amount(3).float(5); // => will give strings with length 9 minimum

zpad(35.582);     // =>  035.58200
zpad(2.48);       // =>  002.48000
zpad(0);          // =>  000.00000
zpad(847.2248);   // =>  847.22480
zpad(5982.493103);// => 5982.493103

zpad.float(null); // no special float treatment, default?
zpad(3.2); // => 3.2
zpad(.2);  // => 0.2

zpad.float(0); // ignores floats
zpad(4.2873); // => 004.2873

So basically, setting zpad.float(0) would give the behavior you desire here. I'm a bit undecided on what to have as the default behavior, though - keep the current one, or use .float(0)?