Your attempt was close, but you forgot to include the generic argument declaration in front of the arrow function parameters. Try something like this:

const log = <T>(message: T): IO<void> =>
   new IO(() => console.log(message));

If you're working in a .tsx file, you may need to do something a little more complex to make it work.

TS will infer the return type automatically as boolean. but also if you want then do this way

const isRandomNumberEven = ():boolean => {
  return Math.round(Math.random() * 100) % 2 === 0;
}

You need no curly brackets, and no this for the console.

this.$scope.$watch(
    () => this.$location.path(),
    value => console.log(value)
);

You can use map in typescript without any type like in JavaScript But if you want to use type, you need to create an interface. Note that object does not have property name , email and other properties, so if you use object the ts compiler raise an error:

Try this one:

interface personlaInfo{
age: number,
gender: string, 
address: string, 
sport: string
}

interface user{
  name:string,
  email: string
  personlaInfo:personlaInfo;
}

var users : Array<user> = [
  {
    name: "John",
    email: "john@msn",
    personlaInfo: {
            age: 56,
            gender: "Male", 
            address: "...", 
            sport: "basketball"
          }
  }  
]

 var f = users.map( (item:user) => (
    { name: item.name,
      email: item.email,
      ...item.personlaInfo
    }
  ));

PlaygroundLink

Simply:

const copy_array2 = (arr) => {
    const cp = [];
    for(let i=0; i < arr.length; i++)
        cp[i] = arr[i];
    return cp;

}

const arr = [1, 2, 3]
const copy = copy_array2(arr)

arr[0] = 5

console.log(copy)

If you want to just convert your arrow functions to regular functions and keep the rest of the code compiling, you can set the target config to es5 and lib property to es6:

"compilerOptions": {
    "target": "es5",
    "lib": ["es6"],
    // ....
}

This will allow your code that uses ES6 features to compile while targeting ES5. But you have to make sure those features (like filter) are available at runtime. If they are not available it will throw runtime exceptions.