ifExpression.js

function ifExpression (condition) {
  if ('function' == typeof condition ? condition() : condition) {
    return {
      then: (callback) => {
        const end = 'function' == typeof callback ? callback() : callback
        const res = {
          else: (callback) => ({
            end
          }),
          elseif: (condition) => ({
            then: (callback) => res
          }),
          end
        }
        return res
      }
    }
  }
  return {
    then: (callback) => {
      return {
        else: (callback) => ({
          end: 'function' == typeof callback ? callback() : callback
        }),
        elseif: (condition) => ifExpression(condition),
        end: null
      }
    }
  }
}