Check out example codes for "arrow function in ts". It will help you in understanding the concepts better.

Code Example 1

// ES6: With arrow function  
var getResult = (username: string, points: number): string => {  
  return `${ username } scored ${ points } points!`;  
};

getResult('joyous jackal' , 100);

Code Example 2

let sum = (x: number, y: number): number => {
    return x + y;
}

sum(10, 20); //returns 30

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