why? compilers for other languages has compile time switches for various checks and/or optimizations, there it is assumed normal. Javascript's "use strict" is just a hack for lack such option. This has some benefits, i.e. you take some codebase that must compile with noImplicitAny and want to add some features, you start with less strict typing (implicit any allowed), when finished you compile with different flag. Because ide (most people use) is recompiling the code all the time there is no reason to clutter this when prototyping. If you don't like this workflow, just use the flag from step 1.