clean-code-javascript

function createMenu(title, body, buttonText, cancellable) {
  // ...
}

function createMenu({ title, body, buttonText, cancellable }) {
  // ...
}

createMenu({
  title: 'Foo',
  body: 'Bar',
  buttonText: 'Baz',
  cancellable: true
});

function emailClients(clients) {
  clients.forEach(client => {
    const clientRecord = database.lookup(client);
    if (clientRecord.isActive()) {
      email(client);
    }
  });
}

function emailClients(clients) {
  clients
    .filter(isClientActive)
    .forEach(email);
}

function isClientActive(client) {
  const clientRecord = database.lookup(client);
  return clientRecord.isActive();
}

function AddToDate(date, month) {
  // ...
}

const date = new Date();

// 뭘 추가하는 건지 이름만 보고 알아내기 힘듭니다.
AddToDate(date, 1);

function AddMonthToDate(date, month) {
  // ...
}

const date = new Date();
AddMonthToDate(date, 1);

function parseBetterJSAlternative(code) {
  const REGEXES = [
    // ...
  ];

  const statements = code.split(' ');
  const tokens = [];
  REGEXES.forEach(REGEX => {
    statements.forEach(statement => {
      // ...
    });
  });

  const ast = [];
  tokens.forEach(token => {
    // lex...
  });

  ast.forEach(node => {
    // parse...
  });
}

function tokenize(code) {
  const REGEXES = [
    // ...
  ];

  const statements = code.split(' ');
  const tokens = [];
  REGEXES.forEach(REGEX => {
    statements.forEach(statement => {
      tokens.push( /* ... */ );
    });
  });

  return tokens;
}

function lexer(tokens) {
  const ast = [];
  tokens.forEach(token => {
    ast.push( /* ... */ );
  });

  return ast;
}

function parseBetterJSAlternative(code) {
  const tokens = tokenize(code);
  const ast = lexer(tokens);
  ast.forEach(node => {
    // parse...
  });
}

function showDeveloperList(developers) {
  developers.forEach(developers => {
    const expectedSalary = developer.calculateExpectedSalary();
    const experience = developer.getExperience();
    const githubLink = developer.getGithubLink();
    const data = {
      expectedSalary,
      experience,
      githubLink
    };

    render(data);
  });
}

function showManagerList(managers) {
  managers.forEach(manager => {
    const expectedSalary = manager.calculateExpectedSalary();
    const experience = manager.getExperience();
    const portfolio = manager.getMBAProjects();
    const data = {
      expectedSalary,
      experience,
      portfolio
    };

    render(data);
  });
}

function showEmployeeList(employees) {
  employees.forEach((employee) => {
    const expectedSalary = employee.calculateExpectedSalary();
    const experience = employee.getExperience();

    let portfolio = employee.getGithubLink();

    if (employee.type === 'manager') {
      portfolio = employee.getMBAProjects();
    }

    const data = {
      expectedSalary,
      experience,
      portfolio
    };

    render(data);
  });
}

const menuConfig = {
  title: null,
  body: 'Bar',
  buttonText: null,
  cancellable: true
};

function createMenu(config) {
  config.title = config.title || 'Foo';
  config.body = config.body || 'Bar';
  config.buttonText = config.buttonText || 'Baz';
  config.cancellable = config.cancellable !== undefined ? config.cancellable : true;
}

createMenu(menuConfig);

const menuConfig = {
  title: 'Order',
  // 유저가 'body' key의 value를 정하지 않았다.
  buttonText: 'Send',
  cancellable: true
};

function createMenu(config) {
  config = Object.assign({
    title: 'Foo',
    body: 'Bar',
    buttonText: 'Baz',
    cancellable: true
  }, config);

  // config는 이제 다음과 동일합니다: {title: "Order", body: "Bar", buttonText: "Send", cancellable: true}
  // ...
}

createMenu(menuConfig);

function createFile(name, temp) {
  if (temp) {
    fs.create(`./temp/${name}`);
  } else {
    fs.create(name);
  }
}

function createFile(name) {
  fs.create(name);
}

function createTempFile(name) {
  createFile(`./temp/${name}`);
}

// 아래 함수에 의해 참조되는 전역 변수입니다.
// 이 전역 변수를 사용하는 또 하나의 함수가 있다고 생각해보세요. 이제 이 변수는 배열이 될 것이고, 프로그램을 망가뜨리겠죠.
let name = 'Ryan McDermott';

function splitIntoFirstAndLastName() {
  name = name.split(' ');
}

splitIntoFirstAndLastName();

console.log(name); // ['Ryan', 'McDermott'];

function splitIntoFirstAndLastName(name) {
  return name.split(' ');
}

const name = 'Ryan McDermott';
const newName = splitIntoFirstAndLastName(name);

console.log(name); // 'Ryan McDermott';
console.log(newName); // ['Ryan', 'McDermott'];

const addItemToCart = (cart, item) => {
  cart.push({ item, date: Date.now() });
};

const addItemToCart = (cart, item) => {
  return [...cart, { item, date : Date.now() }];
};

Array.prototype.diff = function diff(comparisonArray) {
  const hash = new Set(comparisonArray);
  return this.filter(elem => !hash.has(elem));
};

class SuperArray extends Array {
  diff(comparisonArray) {
    const hash = new Set(comparisonArray);
    return this.filter(elem => !hash.has(elem));
  }
}

const programmerOutput = [
  {
    name: 'Uncle Bobby',
    linesOfCode: 500
  }, {
    name: 'Suzie Q',
    linesOfCode: 1500
  }, {
    name: 'Jimmy Gosling',
    linesOfCode: 150
  }, {
    name: 'Gracie Hopper',
    linesOfCode: 1000
  }
];

let totalOutput = 0;

for (let i = 0; i < programmerOutput.length; i++) {
  totalOutput += programmerOutput[i].linesOfCode;
}

const programmerOutput = [
  {
    name: 'Uncle Bobby',
    linesOfCode: 500
  }, {
    name: 'Suzie Q',
    linesOfCode: 1500
  }, {
    name: 'Jimmy Gosling',
    linesOfCode: 150
  }, {
    name: 'Gracie Hopper',
    linesOfCode: 1000
  }
];

const totalOutput = programmerOutput
  .map(programmer => programmer.linesOfCode)
  .reduce((acc, linesOfCode) => acc + linesOfCode, INITIAL_VALUE);

if (fsm.state === 'fetching' && isEmpty(listNode)) {
  // ...
}

function shouldShowSpinner(fsm, listNode) {
  return fsm.state === 'fetching' && isEmpty(listNode);
}

if (shouldShowSpinner(fsmInstance, listNodeInstance)) {
  // ...
}

function isDOMNodeNotPresent(node) {
  // ...
}

if (!isDOMNodeNotPresent(node)) {
  // ...
}

function isDOMNodePresent(node) {
  // ...
}

if (isDOMNodePresent(node)) {
  // ...
}

class Airplane {
  // ...
  getCruisingAltitude() {
    switch (this.type) {
      case '777':
        return this.getMaxAltitude() - this.getPassengerCount();
      case 'Air Force One':
        return this.getMaxAltitude();
      case 'Cessna':
        return this.getMaxAltitude() - this.getFuelExpenditure();
    }
  }
}

class Airplane {
  // ...
}

class Boeing777 extends Airplane {
  // ...
  getCruisingAltitude() {
    return this.getMaxAltitude() - this.getPassengerCount();
  }
}

class AirForceOne extends Airplane {
  // ...
  getCruisingAltitude() {
    return this.getMaxAltitude();
  }
}

class Cessna extends Airplane {
  // ...
  getCruisingAltitude() {
    return this.getMaxAltitude() - this.getFuelExpenditure();
  }
}

function travelToTexas(vehicle) {
  if (vehicle instanceof Bicycle) {
    vehicle.pedal(this.currentLocation, new Location('texas'));
  } else if (vehicle instanceof Car) {
    vehicle.drive(this.currentLocation, new Location('texas'));
  }
}

function travelToTexas(vehicle) {
  vehicle.move(this.currentLocation, new Location('texas'));
}

function combine(val1, val2) {
  if (typeof val1 === 'number' && typeof val2 === 'number' ||
      typeof val1 === 'string' && typeof val2 === 'string') {
    return val1 + val2;
  }
  
  throw new Error('Must be of type String or Number');
}

function combine(val1, val2) {
  return val1 + val2;
}

// 오래된 브라우저의 경우 캐시되지 않은 `list.length`를 통한 반복문은 높은 코스트를 가졌습니다.
// 그 이유는 `list.length`를 매번 계산해야만 했기 때문인데, 최신 브라우저에서는 이것이 최적화 되었습니다.
for (let i = 0, len = list.length; i < len; i++) {
  // ...
}

for (let i = 0; i < list.length; i++) {
  // ...
}

function oldRequestModule(url) {
  // ...
}

function newRequestModule(url) {
  // ...
}

const req = newRequestModule;
inventoryTracker('apples', req, 'www.inventory-awesome.io');

function newRequestModule(url) {
  // ...
}

const req = newRequestModule;
inventoryTracker('apples', req, 'www.inventory-awesome.io');