Rubyist が Javascripter になり始めてやらかしたこと (備忘録) ref: https://qiita.com/ogawatti/items/65a48564f64651ed3574

file0.txt

def hoge
  "hogehoge"
end

hoge  #=> "hogehoge"

file1.js

function hoge() {
  "hogehoge";
};

hoge();  //=> undefined

file10.js

class Baz {
  asyncMyFunc() {
    return new Promise(resolve => {
      setTimeout(() => { resolve("qux");  }, 3000);
    });
  };

  async qux() {
    let val = this.asyncMyFunc();
    console.log(val);  // => Promise { <pending> }

    let val2 = await this.asyncMyFunc();
    console.log(val2);  // => "qux"
  };
};

(new Baz).qux();

file11.js

foo().then(result => {
  bar().then(result => {
    baz().then(result => {
      // ...
    });
  });
});

file12.js

let result
result = await foo()
result = await bar()
result = await baz()

file13.js

async function piyo() {
  await asyncFunc()
}
piyo()

file14.txt

Foo.new.three  #=> 3
class Foo
  def three; "3"; end
end
Foo.new.three  #=> "3"

file15.js

(new Foo).three();  //=> 3
Foo.prototype.three = function() { return "3" };
(new Foo).three();  //=> "3"

file16.js

const expect = require('chai').expect
describe('Foo', () => {
  beforeEach(() => {
    // ...
  })
  let foo = new Foo

  describe('#hoge()', () => {
    it ('return "hogehoge"', () => {
      expect(foo.hoge()).to.equal("hogehoge");
    });
  });

  // 非同期関数のテスト
  describe('#fuga()', () => {
    it ('return "hogehoge"', async () => {
      expect(await foo.fuga()).to.equal("fugafuga");
    });
  });

  // shared_example 的に使える
  function piyo() {
    it ('return "piyopiyo"', () => {
      expect(Foo.piyo()).to.equal("piyopiyo");
    });
  };

  describe('#piyo()', piyo);

  context('when ...', () => {
    // ...
  });
});

file17.txt

$ ./node_modules/.bin/mocha 


  Foo
    #hoge()
      ✓ return "hogehoge"
    #fuga()
      ✓ return "hogehoge" (1006ms)
    #piyo()
      ✓ return "piyopiyo"


  3 passing (1s)

file2.txt

def func(*args)
  p args  #=> ["a", "b", "c"]
end
func('a', 'b', 'c')

file3.js

function func(...args) {
  console.log(args)
}
func('a', 'b', 'c')  //=> [ 'a', 'b', 'c' ]

file4.txt

class Array
  def forEach(func)
    self.each do |n|
      func.call(n)
    end
  end
end

[1, 2, 3].forEach(lambda {|n|
  puts n
})

file5.js

[1, 2, 3].forEach((n) => {
  console.log(n);
});

file6.txt

class Foo
  def three; 3; end

  def bar
    [1, 2, 3].each do |n|
      puts n * self.three  #=> 3, 6, 9
    end
  end
end

Foo.new.bar

file7.js

class Foo {
  three() { return 3; };

  bar() {
    /*
    [1, 2, 3].forEach(function(n) {
      console.log(n * this.three());  //=> TypeError: Cannot read property 'three' of undefined
    });
    */

    // 関数式にthisを指定する
    [1, 2, 3].forEach(function(n) {
      console.log(n * this.three());  //=> 3, 6, 9
    }, this);

    // アロー関数を使う
    [1, 2, 3].forEach(n => {
      console.log(n * this.three());  //=> 3, 6, 9
    });
  }
}

(new Foo).bar()

file8.txt

sleep(3)

file9.js

setTimeout(() => {}, 3000);