npm install babel-statictype-plugin
{
"plugins":["babel-statictype-plugin"]
}
//in your code('xx' is a custom name,also u can catch up with the example)
let Num_xx; // number
let Str_xx; //string
let Bool_xx; // boolean
let Obj_xx; // object
let Null_xx; //null
let Und_xx; //undefined
let Sym_xx; //Symbol
function foo(Num_a,Str_b){
}
foo(1,'a') // won't throw an error
foo(1,1) // will throw an error,cause second 1 is not a string-type value