Ts-loader: Why we need babel if we can use `tsc` to convert `es6` to `es5`?

[chenzhutian]

As my understanding, I can use tsc to convert es6 to es5. The only constraint is that the file extension of the script to be converted must be .ts or .tsx.
Can ts-loader provide an option so that we can convert .js file by using tsc?
By doing so, I can no longer need to install too many devDependences modules of babel.

[johnnyreilly]

Babel is necessary if you want to polyfill new APIs like Promise, Map etc. If you don't use those then you don't need babel