Convert between Camel Case (camelCase) and Snake Case (snake_case) in ES6

case.js

export const toCamelCase = (e) => {
  return e.replace(/_([a-z])/g, (g) =>  g[1].toUpperCase());
};

export const toSnakeCase = (e) => {
  return e.match(/([A-Z])/g).reduce(
    (str, c) => str.replace(new RegExp(c), '_' + c.toLowerCase()),
    e
  )
  .substring((e.slice(0, 1).match(/([A-Z])/g)) ? 1 : 0);
};

Thanks, this is great!

One FYI - for isSnakeCase, the reduce will fail if the input is already in snake case (e.g. toSnakeCase('foo'), toSnakeCase('foo_bar'). I added

if (e.toLowerCase() === e) {
    return e;
}

at the start, but there's probably a more elegant way.