释放双眼，带上耳机，听听看~！
容导航
- dart:core – numbers, collections, strings, and more
- dart:async – asynchronous programming
- dart:math – math and random
- dart:html – browser-based apps
- dart:io – I/O for command-line apps
- dart:convert – decoding and encoding JSON, UTF-8, and more
- dart:mirrors – reflection
- Summary
http://dart.goodev.org/guides/libraries/library-tour\#dartcore—numbers-collections-strings-and-more
