Well, Jane Street found Ocaml's standard library lacking and went on to build a better one. To me it seems much better than build a "standard library" piece-by-piece from one-function packages.
My understanding is that Lodash started as a replacement for Underscore.js and was originally fairly monolithic. Only in the most recent version do they make it so that each function is separately requirable and published. They have modularized after starting monolithically (without verifying, I also think that Lodash develops in a single repository, but publishes a bunch of modules from that one repo).
It even includes a function for padding strings. I think you would be doing better for yourself using lodash over left-pad, and the cost of including a bigger library on server-side JS is negligible.