Migrate to TypeScript

Author: whymarrh

.babelrc

@@ -0,0 +1,3 @@
+{
+  "extends": "@ethereumjs/config-nyc"
+}

.nycrc

@@ -0,0 +1,5 @@
+node_modules
+.vscode
+package.json
+dist
+.nyc_output

.prettierignore

@@ -1,69 +1,78 @@
 # Changelog
+
 All notable changes to this project will be documented in this file.
 
-The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) 
-(modification: no type change headlines) and this project adheres to 
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+(modification: no type change headlines) and this project adheres to
 [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
-
 ## [3.4.0] - 2019-02-06
-**Petersburg** (aka `constantinopleFix`) as well as **Goerli** 
-support/readiness by updating to a supporting `ethereumjs-common` version 
-[v1.1.0](https://github.com/ethereumjs/ethereumjs-common/releases/tag/v1.1.0), 
+
+**Petersburg** (aka `constantinopleFix`) as well as **Goerli**
+support/readiness by updating to a supporting `ethereumjs-common` version
+[v1.1.0](https://github.com/ethereumjs/ethereumjs-common/releases/tag/v1.1.0),
 PR [#86](https://github.com/ethereumjs/ethereumjs-blockchain/pull/86)
 
 [3.4.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v3.3.3...v3.4.0
 
 ## [3.3.3] - 2019-01-03
-- Fixed a bug causing the ``iterate()`` method to fail when an older version
-  ``levelup`` DB instance is passed, see PR [#83](https://github.com/ethereumjs/ethereumjs-blockchain/pull/83)
+
+-   Fixed a bug causing the `iterate()` method to fail when an older version
+    `levelup` DB instance is passed, see PR [#83](https://github.com/ethereumjs/ethereumjs-blockchain/pull/83)
 
 [3.3.3]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v3.3.2...v3.3.3
 
 ## [3.3.2] - 2018-12-20
-- Updated ``levelup`` dependency to ``level-mem`` ``v3.0.1``, PR [#75](https://github.com/ethereumjs/ethereumjs-blockchain/pull/75)
-- Fix ``putBlock()`` edge case, PR [#79](https://github.com/ethereumjs/ethereumjs-blockchain/pull/79)
-- Replaced uses of deprecated `new Buffer` with `Buffer.from`, PR [#80](https://github.com/ethereumjs/ethereumjs-blockchain/pull/80)
+
+-   Updated `levelup` dependency to `level-mem` `v3.0.1`, PR [#75](https://github.com/ethereumjs/ethereumjs-blockchain/pull/75)
+-   Fix `putBlock()` edge case, PR [#79](https://github.com/ethereumjs/ethereumjs-blockchain/pull/79)
+-   Replaced uses of deprecated `new Buffer` with `Buffer.from`, PR [#80](https://github.com/ethereumjs/ethereumjs-blockchain/pull/80)
 
 [3.3.2]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v3.3.1...v3.3.2
 
 ## [3.3.1] - 2018-10-26
-- Replaced calls to BN.toBuffer() with BN.toArrayLike() so that ``ethereumjs-blockchain`` can run in a browser environment, PR [#73](https://github.com/ethereumjs/ethereumjs-blockchain/pull/73)
+
+-   Replaced calls to BN.toBuffer() with BN.toArrayLike() so that `ethereumjs-blockchain` can run in a browser environment, PR [#73](https://github.com/ethereumjs/ethereumjs-blockchain/pull/73)
 
 [3.3.1]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v3.3.0...v3.3.1
 
 ## [3.3.0] - 2018-10-19
-- Constantinople support when using block validation (set with ``opts.validate`` in constructor),
- update to a Constantinople-ready version of the ``ethereumjs-block`` dependency (>2.1.0), PR [#71](https://github.com/ethereumjs/ethereumjs-blockchain/pull/71)
+
+-   Constantinople support when using block validation (set with `opts.validate` in constructor),
+    update to a Constantinople-ready version of the `ethereumjs-block` dependency (>2.1.0), PR [#71](https://github.com/ethereumjs/ethereumjs-blockchain/pull/71)
 
 [3.3.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v3.2.1...v3.3.0
 
 ## [3.2.1] - 2018-08-29
-- Fixed an issue with the ``iterator()`` function returning an error on end of block iteration instead of finish gracefully, PR [#64](https://github.com/ethereumjs/ethereumjs-blockchain/pull/64)
-- Updated ``ethereumjs-common`` dependency to ``v0.5.0`` (custom chain support), PR [#63](https://github.com/ethereumjs/ethereumjs-blockchain/pull/63)
+
+-   Fixed an issue with the `iterator()` function returning an error on end of block iteration instead of finish gracefully, PR [#64](https://github.com/ethereumjs/ethereumjs-blockchain/pull/64)
+-   Updated `ethereumjs-common` dependency to `v0.5.0` (custom chain support), PR [#63](https://github.com/ethereumjs/ethereumjs-blockchain/pull/63)
 
 [3.2.1]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v3.2.0...v3.2.1
 
 ## [3.2.0] - 2018-08-13
-- Added support for setting network and performing hardfork-specific validation by integrating with [ethereumjs-common](https://github.com/ethereumjs/ethereumjs-common), PR [#59](https://github.com/ethereumjs/ethereumjs-blockchain/pull/59)
-- Added ``Blockchain.putHeader()`` and ``Blockchain.putHeaders()`` functions to provide header-chain functionality (needed by ethereumjs-client), PR [#59](https://github.com/ethereumjs/ethereumjs-blockchain/pull/59)
-- Fixed a bug with caching, PR [#59](https://github.com/ethereumjs/ethereumjs-blockchain/pull/59)
-- Fixed error propagation in ``Blockchain.iterator()``, PR [#60](https://github.com/ethereumjs/ethereumjs-blockchain/pull/60)
+
+-   Added support for setting network and performing hardfork-specific validation by integrating with [ethereumjs-common](https://github.com/ethereumjs/ethereumjs-common), PR [#59](https://github.com/ethereumjs/ethereumjs-blockchain/pull/59)
+-   Added `Blockchain.putHeader()` and `Blockchain.putHeaders()` functions to provide header-chain functionality (needed by ethereumjs-client), PR [#59](https://github.com/ethereumjs/ethereumjs-blockchain/pull/59)
+-   Fixed a bug with caching, PR [#59](https://github.com/ethereumjs/ethereumjs-blockchain/pull/59)
+-   Fixed error propagation in `Blockchain.iterator()`, PR [#60](https://github.com/ethereumjs/ethereumjs-blockchain/pull/60)
 
 [3.2.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v3.1.0...v3.2.0
 
 ## [3.1.0] - 2018-05-24
-- New ``getLatestHeader()`` and ``getLatestBlock()`` methods for retrieving the latest header
-  respectively full block in the canonical chain, PR [#52](https://github.com/ethereumjs/ethereumjs-blockchain/pull/52)
-- Fixed ``saveHeads()`` bug not storing the internal ``headHeader``/``headBlock`` header cursors
-  to the DB, PR [#52](https://github.com/ethereumjs/ethereumjs-blockchain/pull/52)
-- Updated API docs
+
+-   New `getLatestHeader()` and `getLatestBlock()` methods for retrieving the latest header
+    respectively full block in the canonical chain, PR [#52](https://github.com/ethereumjs/ethereumjs-blockchain/pull/52)
+-   Fixed `saveHeads()` bug not storing the internal `headHeader`/`headBlock` header cursors
+    to the DB, PR [#52](https://github.com/ethereumjs/ethereumjs-blockchain/pull/52)
+-   Updated API docs
 
 [3.1.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v3.0.0...v3.1.0
 
 ## [3.0.0] - 2018-05-18
+
 This release comes with heavy internal changes bringing Geth DB compatibility to the
-``ethereumjs-blockchain`` library. For a full list of changes and associated discussion
+`ethereumjs-blockchain` library. For a full list of changes and associated discussion
 see PR [#47](https://github.com/ethereumjs/ethereumjs-blockchain/pull/47)
 (thanks to @vpulim for this amazing work!). To test iterating through your local Geth
 chaindata DB you can run the [example](https://github.com/ethereumjs/ethereumjs-blockchain#example)
@@ -76,64 +85,69 @@ instances, so it is not possible to load an old DB with the new library version
 problems for you get in touch on GitHub or Gitter!).
 
 Summary of the changes:
-- New unified constructor where ``detailsDB`` and ``blockDB`` are replaced by a single ``db`` reference
-- Deprecation of the ``getDetails()`` method now returning an empty object
-- ``td`` and ``height`` are not stored in the db as meta info but computed as needed
-- Block headers and body are stored under two separate keys
-- Changes have been made to properly rebuild the chain and number/hash mappings as a result of forks and deletions
-- A write-through cache has been added to reduce database reads
-- Similar to geth, we now defend against selfish mining vulnerability 
-- Added many more tests to increase coverage to over 90%
-- Updated docs to reflect the API changes
-- Updated library dependencies
+
+-   New unified constructor where `detailsDB` and `blockDB` are replaced by a single `db` reference
+-   Deprecation of the `getDetails()` method now returning an empty object
+-   `td` and `height` are not stored in the db as meta info but computed as needed
+-   Block headers and body are stored under two separate keys
+-   Changes have been made to properly rebuild the chain and number/hash mappings as a result of forks and deletions
+-   A write-through cache has been added to reduce database reads
+-   Similar to geth, we now defend against selfish mining vulnerability
+-   Added many more tests to increase coverage to over 90%
+-   Updated docs to reflect the API changes
+-   Updated library dependencies
 
 [3.0.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v2.1.0...v3.0.0
 
 ## [2.1.0] - 2017-10-11
-- ``Metro-Byzantium`` compatible
-- Updated ``ethereumjs-block`` dependency (new difficulty formula / difficulty bomb delay)
+
+-   `Metro-Byzantium` compatible
+-   Updated `ethereumjs-block` dependency (new difficulty formula / difficulty bomb delay)
 
 [2.1.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v2.0.2...v2.1.0
 
 ## [2.0.2] - 2017-09-19
-- Tightened dependencies to prevent the ``2.0.x`` version of the library to break
-  after ``ethereumjs`` Byzantium library updates
+
+-   Tightened dependencies to prevent the `2.0.x` version of the library to break
+    after `ethereumjs` Byzantium library updates
 
 [2.0.2]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v2.0.1...v2.0.2
 
 ## [2.0.1] - 2017-09-14
-- Fixed severe bug adding blocks before blockchain init is complete
+
+-   Fixed severe bug adding blocks before blockchain init is complete
 
 [2.0.1]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v2.0.0...v2.0.1
 
 ## [2.0.0] - 2017-01-01
-- Split ``db`` into ``blockDB`` and ``detailsDB`` (breaking)
+
+-   Split `db` into `blockDB` and `detailsDB` (breaking)
 
 [2.0.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.4.2...v2.0.0
 
 ## [1.4.2] - 2016-12-29
-- New ``getBlocks`` API method
-- Testing improvements
+
+-   New `getBlocks` API method
+-   Testing improvements
 
 [1.4.2]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.4.1...v1.4.2
 
 ## [1.4.1] - 2016-03-01
-- Update dependencies to support Windows
+
+-   Update dependencies to support Windows
 
 [1.4.1]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.4.0...v1.4.1
 
 ## [1.4.0] - 2016-01-09
-- Bump dependencies
 
-[1.4.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.3.4...v1.4.0
+-   Bump dependencies
 
+[1.4.0]: https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.3.4...v1.4.0
 
 ## Older releases:
 
-- [1.3.4](https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.3.3...v1.3.4) - 2016-01-08
-- [1.3.3](https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.3.2...v1.3.3) - 2015-11-27
-- [1.3.2](https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.3.1...v1.3.2) - 2015-11-27
-- [1.3.1](https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.2.0...v1.3.1) - 2015-10-23
-- 1.2.0 - 2015-10-01
-
-
+-   [1.3.4](https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.3.3...v1.3.4) - 2016-01-08
+-   [1.3.3](https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.3.2...v1.3.3) - 2015-11-27
+-   [1.3.2](https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.3.1...v1.3.2) - 2015-11-27
+-   [1.3.1](https://github.com/ethereumjs/ethereumjs-blockchain/compare/v1.2.0...v1.3.1) - 2015-10-23
+-   1.2.0 - 2015-10-01