fix(type): add promise missing typings and simplify code

[yuxizhe]

add promise wrapper missing typings and simplify code.

fix #1184 #804

[sidorares]

lgtm @yuxizhe , thanks for working on this.

Would you be able to add a simple test harness for typings? ( something as simple as tsc test.ts ) if not happy to merge as is

[yuxizhe]

@sidorares Sure, I will add typings test for this.

[jmordica]

@sidorares Sure, I will add typings test for this.

I can add the test if you aren't able to @yuxizhe?

[yuxizhe]

@sidorares Sure, I will add typings test for this.

I can add the test if you aren't able to @yuxizhe?

@jmordica Welcome, Thank you very much!

[sidorares]

Thsnks @jmordica currently there is zero checks for the validity of the typings, even the most basic one would be a great addition

[jmordica]

@sidorares this can be closed in lieu of #1610