what does `(this as any)` mean in this typescript snippet?

It can be actually written as

 (<any>this)[transport](item);

The type casting is exhibited in the above statement!

(this as any ) is just a Type Assertion that works on dev/compiling time and has no side effects on run time because it is purely a Typescript thing. It can be useful if something related to this like this[whatever] which outputs a TS error because whatever is not defined inside the this TS type. So, this error can be suppressed with (this as any)[whatever]

Also (this as any) is the equivalent to (<any> this)

Note to mention: --suppressImplicitAnyIndexErrors as a compiler option suppresses those kind of possible errors.