Function Composition

Getting functions to work together is function composition. 

const uppercaseString = (string) => string.toUpperCase(); 
const reverseString = (string) => string.split("").reverse().join("");  

const upperAndReverseName = (string) => { 
  const upperCasedName = uppercaseString(name); 
  return reverseString(upperCasedName); 
}; 

const name ="John"; 
const result = upperAndReverseName(name);

console.log({ result }); // { result: "NHOJ" }


// Beauty of Function Composition 
Now let us consider the scenario where you have list of names. 

const uppercaseString = (string) => string.toUpperCase(); 
const reverseString = (string) => string.split("").reverse().join("");  

const upperAndReverseName = (string) => { 
  const upperCasedName = uppercaseString(string); 
  return reverseString(upperCasedName); 
}; 

const upperAndReverseNameAll = (names) => { 
  return names.map(upperAndReverseName); 
}

const names = [ "John", "Gary", "Stark" ];  
const result = upperAndReverseNameAll(names); 

console.log({ result }); // { [ "NHOJ", "YRAG", "KRATS" ] }