ndc9e1f52d75d.after.ts

// 1. TypeScriptで書く
type Person = {
  favoriteColor: string;
  name: string;
  age: number;
};

// 2. Overloadも書ける
function makePerson(favoriteColor: string, name: string, age: number): Person;
function makePerson(name: string, age: number): Person;

// 3. インデントは揃える
function makePerson(favoriteColorOrName: string, nameOrAge: string | number, age?: number): Person {
  // 4. 早期リターンを心がける
  if ((age !== undefined) && (typeof nameOrAge === "string")) {
    return {
      favoriteColor: favoriteColorOrName,
      name: nameOrAge,
      age,
    };
  }

  if ((age === undefined) && (typeof nameOrAge === "number")) {
    return {
      favoriteColor: "green",
      name: favoriteColorOrName,
      age: nameOrAge,
    };
  }

  throw new Error("unexpected use of function");
};
  
const person = makePerson("Joe", 18);

// 5. ログは見やすい形で出力する
console.log({ person });

ndc9e1f52d75d.before.js

var makePerson = function(favoriteColor, name, age) {
  if (arguments.length < 3) {
      favoriteColor = "green";
      name = arguments[0];
      age = arguments[1];
  }
  
  return {
              name: name,
              age: age,
              favoriteColor: favoriteColor
          };
  };
  
  var person = makePerson("Joe", 18);
  console.log(JSON.stringify(person));