typescript_talk

code for "Making Javascript Illegal States Unrepresentable" talk

step zero: no restrictions

• all calls are valid
• there are a lot of valid calls
• no checks of any kind: Math.Pi, Math.round arguments, our own arguments
• ES5 transpiling (number notation, backtick strings)

step one: checkJs:true

• some simple argument calls are no longer valid
• no longer 65535 parameter calls.
• how does arguments use changes that? (taste of "control flow analysis")
• how does ...params change that? (+ ES5 transpiling for .. of)
• no arguments calls are valid, all parameters are optional
• checks for Math.Pi and Math.round arguments
• additional checks like noUnusedParameters

step two: Typescript as a superset

• just a single character change on the file name main.js => main.ts
• all previous invalid states are invalid here too (Math.Pi)
• extra parameters break single param invocations (no more optionals)
• extra checks like noUnusedParameters are still valid