snake_case to camelCase

What it's for

The same name written two different ways is daily bread for anyone who codes: a database speaks snake_case (birth_date), JavaScript speaks camelCase (birthDate), and in between there's always someone retyping dozens of names by hand. Here you paste the whole list and the conversion happens to all of it at once: the underscore disappears and the letter that followed it becomes a capital.

How it works

There's a single rule and it applies everywhere in the text: every run of underscores is removed and the letter or digit right after it becomes uppercase. So user__name becomes userName even with two underscores in a row. The rest of the text isn't touched, so you can paste a whole file and not just the names: commas, brackets and line breaks stay where they are.

Two cases where the result needs a look

The first is constants in capitals. From USER_NAME you get USERName, which is what nobody wanted: the page doesn't lower the capitals it already finds, because doing so would ruin acronyms sitting inside names. If you're converting constants, put them all in lowercase first with Upper and lowercase.

The second is the leading underscore, which in many languages means «internal, don't touch»: _private becomes Private and that meaning is lost. It's only a handful of names, but it's the kind of detail that later costs you half an hour.

Nearby tools

The opposite direction is camelCase → snake_case. If instead you need the name for a web address, with ordinary dashes in place of spaces, the page is Make a URL slug. For freer replacements, with you deciding the rule, there is Find and replace.