Steps to Convert to TypeScript

What not to do

• functional changes at the same time
• attempt this with low test coverage
• aimming for perfect - don't try to type things too strongly in the beginning
• forget to add tests for your types - dtslint for testing types
• publish types for consumer use when they are in "weak" state

1. Compiling in "loose mode"

• start with tests passing
• rename all .js to .ts, allowing implicit any
• fix only the things that are not type-checking, or cauing compile errors
• be careful to avoid changing behavior
• get tests passing again

2. Explicit Any
   • start with tests passing
   • ban implicit any "noImplicitAny" : true
   • where possible, provide a specific and appropriate type
     • import types for dependences from DefinitelyTyped
     • otherwise explicit any
   • get tests passing again
3. Squash explicit anys, enable strict mode
   • incrementally, in small chunks...
   • enable strict mode

   "strictNullChecks": true, // the only thing that can hold null is null
   "strict": true,
   "strictFunctionTypes": true, // validates arguments and return types of return types 
   "strictBindCallAppy": true // make sure the arguments passed to bind, call, apply and the lexical scope all type check appropriates
   

   • replace explicit anys with more appropriated types
   • try really hard to avoid unsafe casts