The first thing to know is that typescript needs to be compiled by the typescript transcompiler. There are a number of ways to get the compiler. You can install it as part of a node.js install using npm, the node package manager. You can download the visual studio plugin or you can compile it from source. Compile it from source? What is this, linux? Actually the compiler is written in typescript. I guess that this is a pretty common thing to do when you build a compiler: build a minimal compiler and then use that to build a more fully featured compiler. It boggles my mind, to be perfectly honest.
Anyway, I installed the npm version because Iâ€™m doing most of my web development using the Sublime text editor. The command line is very easy, you can pretty much get away with knowing
./tsc blah.ts -out thisisabadidea.js
There are a number of other flags you can use including a bunch of undocumented flags youâ€™ll only find by reading the source. The most useful flag is -w which watches the .ts file and recompiles it when there are changes. This is useful if youâ€™re developing you code and donâ€™t want to have to keep dropping to the command line to recompile and then refresh in the browser.
If we change the call to this function to
Then try to compile it typescript will throw an error
Supplied parameters do not match any signature of call target
This is obviously a very simple example but I have found that typescript quickly pulls out silly typing errors which normally I would have to check with unit tests.
Tomorrow weâ€™ll look into some more features of typescript.