Node.js でコンソールを使用する方法についての簡単な説明

const authorsAndBooks = [['Tolkien', 'Lord of The Rings'],['Rutger', 'Utopia For Realists'], ['Sinek', 'Leaders Eat Last'], ['Eyal', 'Habit']];
console.table(authorsAndBooks);

const inventory = { apples: 200, mangoes: 50, avocados: 300, kiwis: 50 };
console.table(inventory);

const forexConverter = { asia: { rupee: 1.39, renminbi: 14.59 , ringgit: 24.26 }, africa: { rand: 6.49, nakfa: 6.7 , kwanza:0.33 }, europe: { swissfranc: 101.60, gbp: 130, euro: 115.73 } };
console.table(forexConverter);

const workoutLog = { Monday: { push: 'Incline Bench Press', pull: 'Deadlift'}, Wednesday: { push: 'Weighted Dips', pull: 'Barbell Rows'}};
console.table(workoutLog);

console.table(workoutLog, 'push');

console.dir(object, options);
// where options = { showHidden: true ... }

const user = {
  details: {
    name: {
      firstName: 'Immanuel',
      lastName: 'Kant'
    },
    height: `1.83m"`,
    weight: '90kg',
    age: '80',
    occupation: 'Philosopher',
    nationality: 'German',
    books: [
      {
        name: 'Critique of Pure Reason',
        pub: '1781',
      },
      {
        name: 'Critique of Judgement',
        pub: '1790',
      },
      {
        name: 'Critique of Practical Reason',
        pub: '1788',
      },
      {
        name: 'Perpetual Peace',
        pub: '1795',
      },
    ],
    death: '1804'
  }
}

console.dir(user);

console.dirxml(object|nodeList);

const toc = document.querySelector('#toc');
console.dirxml(toc);

console.dirxml(document)

console.assert(value, [...messages])

console.assert(false, 'Assertion failed');

OutputAssertion failed: Assertion failed

const sum = (a = 0, b = 0) => Number(a) + Number(b);

function test(functionName, actualFunctionResult, expected) {
  const actual = actualFunctionResult;
  const pass = actual === expected;
  console.assert(pass, `Assertion failed for ${functionName}`);
  return `Test passed ${actual} === ${expected}`;
}

console.log(test('sum', sum(1,1), 2)); // Test passed 2 === 2
console.log(test('sum', sum(), 0));    // Test passed 0 === 0
console.log(test('sum', sum, 2));      // Assertion failed for sum
console.log(test('sum', sum(3,3), 4)); // Assertion failed for sum

console.warn(string, substitution);

console.error(string, substitution);

const sum = (a = 0, b = 0) => Number(a) + Number(b);

function otherTest(actualFunctionResult, expected) {
  if (actualFunctionResult !== expected) {
    console.error(new Error(`Test failed ${actualFunctionResult} !== ${expected}`));
  } else {
    // pass
  }
}

otherTest(sum(1,1), 3);

function getCapital(country) {
  const capitalMap = {
    belarus: 'minsk', australia: 'canberra', egypt: 'cairo', georgia: 'tblisi', latvia: 'riga', samoa: 'apia'
  };
  console.trace('Start trace here');
  return Object.keys(capitalMap).find(item => item === country) ? capitalMap[country] : undefined;
}

console.log(getCapital('belarus'));
console.log(getCapital('accra'));

const getOccurences = (word = 'foolish') => {
  const phrase = `Oh me! Oh life! of the questions of these recurring, Of the endless trains of the faithless, of cities fill’d with the foolish, Of myself forever reproaching myself, for who more foolish than I, and who more faithless?`;

  let count = 0;
  const wordsFromPhraseArray = phrase.replace(/[,.!?]/igm, '').split(' ');
  wordsFromPhraseArray.forEach((element, idx) => {
    if (element === word) {
      count ++;
      console.count(word);
    }
  });
  return count;
}

getOccurences();

[secondary_label]
foolish: 1
foolish: 2
2

const getOccurences = (word = 'foolish') => {
  const phrase = `Oh me! Oh life! of the questions of these recurring, Of the endless trains of the faithless, of cities fill’d with the foolish, Of myself forever reproaching myself, for who more foolish than I, and who more faithless?`;

  let count = 0;
  const wordsFromPhraseArray = phrase.replace(/[,.!?]/igm, '').split(' ');
  wordsFromPhraseArray.forEach((element, idx) => {
    if (element === word) {
      count ++;
      console.count(word);
      console.countReset(word);
    }
  });
  return count;
}

getOccurences();

[secondary_label]
foolish: 1
foolish: 1
2

console.time(&#39;<timer-label>&#39;);
console.timeEnd(&#39;<timer-label>&#39;);

const users = ['Vivaldi', 'Beethoven', 'Ludovico'];

const loop = (array) => {
  array.forEach((element, idx) => {
    console.log(element);
  })
}

const timer = () => {
  console.time('timerLabel');
  loop(users);
  console.timeEnd('timerLabel');
}

timer();

OutputVivaldi
Beethoven
Ludovico
timerLabel: 0.69091796875ms