change-string-case/node_modules/before-after-hook/lib/add.js

module.exports = addHook

function addHook (state, kind, name, hook) {
  var orig = hook
  if (!state.registry[name]) {
    state.registry[name] = []
  }

  if (kind === 'before') {
    hook = function (method, options) {
      return Promise.resolve()
        .then(orig.bind(null, options))
        .then(method.bind(null, options))
    }
  }

  if (kind === 'after') {
    hook = function (method, options) {
      var result
      return Promise.resolve()
        .then(method.bind(null, options))
        .then(function (result_) {
          result = result_
          return orig(result, options)
        })
        .then(function () {
          return result
        })
    }
  }

  if (kind === 'error') {
    hook = function (method, options) {
      return Promise.resolve()
        .then(method.bind(null, options))
        .catch(function (error) {
          return orig(error, options)
        })
    }
  }

  state.registry[name].push({
    hook: hook,
    orig: orig
  })
}