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ã¯ã©ã¹ã®ä½¿ç¨ - JavaScript | MDN

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const bigDay = new Date(2019, 6, 19);
console.log(bigDay.toLocaleDateString());
if (bigDay.getTime() < Date.now()) {
  console.log("Once upon a time...");
}

æåã®è¡ã§ã¯ãã¯ã©ã¹ Date ã®ã¤ã³ã¹ã¿ã³ã¹ãä½æããbigDay ã¨åä»ãã¦ãã¾ãã2 è¡ç®ã§ã¯ãbigDay ã¤ã³ã¹ã¿ã³ã¹ã«å¯¾ãã¦ ã¡ã½ãã toLocaleDateString() ãå¼ã³åºãã¦ãæååãè¿ãã¦ãã¾ããæ¬¡ã«ã2 ã¤ã®æ°å¤ãæ¯è¼ãã¦ãã¾ãã1 ã¤ã¯ getTime() ã¡ã½ããããè¿ããããã®ããã 1 ã¤ã¯ Date ã¯ã©ã¹èªä½ãã Date.now() ã¨ãã¦ç´æ¥å¼ã³åºããããã®ã§ãã

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ã¯ã©ã¹ã¯ãµã¤ããã¯ã©ã¹å®£è¨ã§ä½æããã¾ãã

class MyClass {
  // ã¯ã©ã¹æ¬ä½...
}

ã¯ã©ã¹æ¬ä½ã®ä¸ã§ãå©ç¨ã§ããæ©è½ã¯å¤å²ã«ãããã¾ãã

class MyClass {
  // ã³ã³ã¹ãã©ã¯ã¿ã¼
  constructor() {
    // ã³ã³ã¹ãã©ã¯ã¿ã¼ã®æ¬ä½
  }
  // ã¤ã³ã¹ã¿ã³ã¹ãã£ã¼ã«ã
  myField = "foo";
  // ã¤ã³ã¹ã¿ã³ã¹ã¡ã½ãã
  myMethod() {
    // myMethod æ¬ä½
  }
  // éçãã£ã¼ã«ã
  static myStaticField = "bar";
  // éçã¡ã½ãã
  static myStaticMethod() {
    // myStaticMethod æ¬ä½
  }
  // éçãããã¯
  static {
    // éçåæåã³ã¼ã
  }
  // ãã£ã¼ã«ããã¡ã½ãããéçãã£ã¼ã«ããéçã¡ã½ããã«ã¯ããã¹ã¦
  // ããã©ã¤ãã¼ããå½¢å¼ãããã¾ã
  #myPrivateField = "bar";
}

function MyClass() {
  this.myField = "foo";
  // ã³ã³ã¹ãã©ã¯ã¿ã¼æ¬ä½
}
MyClass.myStaticField = "bar";
MyClass.myStaticMethod = function () {
  // myStaticMethod æ¬ä½
};
MyClass.prototype.myMethod = function () {
  // myMethod æ¬ä½
};

(function () {
  // éçåæåã³ã¼ã
})();

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const myInstance = new MyClass();
console.log(myInstance.myField); // 'foo'
myInstance.myMethod();

const myInstance = MyClass(); // TypeError: Class constructor MyClass cannot be invoked without 'new'

ã¯ã©ã¹å®£è¨ã®å·»ãä¸ã

new MyClass(); // ReferenceError: Cannot access 'MyClass' before initialization

class MyClass {}

ãã®åä½ã¯ãlet ã const ã§å®£è¨ããå¤æ°ã¨ä¼¼ã¦ãã¾ãã

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const MyClass = class {
  // Class body...
};

const MyClass = class MyClassLongerName {
  // ã¯ã©ã¹æ¬ä½ãããã§ã¯ãMyClass ã¨ MyClassLongerName ã¯åãã¯ã©ã¹ãæãã¦ãã¾ãã
};
new MyClassLongerName(); // ReferenceError: MyClassLongerName is not defined

ã³ã³ã¹ãã©ã¯ã¿ã¼

class Color {
  constructor(r, g, b) {
    // RGB å¤ã `this` ã®ããããã£ã¨ãã¦å²ãå½ã¦ãã
    this.values = [r, g, b];
  }
}

const red = new Color(255, 0, 0);
console.log(red);

ãã®ãããªåºåãç¢ºèªã§ããã¯ãã§ãã

Object { values: (3) [â¦] }
  values: Array(3) [ 255, 0, 0 ]

function createColor(r, g, b) {
  return {
    values: [r, g, b],
  };
}

class Color {
  constructor(...values) {
    this.values = values;
  }
}

const red = new Color(255, 0, 0);
// ä¸è¨ã¨åãå½¢ç¶ã®ã¤ã³ã¹ã¿ã³ã¹ãä½æãã¾ãã

new ãå¼ã³åºããã³ã«ãç°ãªãã¤ã³ã¹ã¿ã³ã¹ãä½æããã¾ãã

const red = new Color(255, 0, 0);
const anotherRed = new Color(255, 0, 0);
console.log(red === anotherRed); // false

class MyClass {
  constructor() {
    this.myField = "foo";
    return {};
  }
}

console.log(new MyClass().myField); // undefined

ã¤ã³ã¹ã¿ã³ã¹ã¡ã½ãã

class Color {
  constructor(r, g, b) {
    this.values = [r, g, b];
  }
  getRed() {
    return this.values[0];
  }
}

const red = new Color(255, 0, 0);
console.log(red.getRed()); // 255

class Color {
  constructor(r, g, b) {
    this.values = [r, g, b];
    this.getRed = function () {
      return this.values[0];
    };
  }
}

ããã¯ãã¾ãåä½ãã¾ããããããåé¡ã¯ãColorã¤ã³ã¹ã¿ã³ã¹ãä½æããããã³ã«ããã¹ã¦åããã¨ãããã«ãããããããæ°ããé¢æ°ãä½æããããã¨ã§ãã

console.log(new Color().getRed === new Color().getRed); // false

class Color {
  constructor(r, g, b) {
    this.values = [r, g, b];
  }
  getRed() {
    return this.values[0];
  }
  setRed(value) {
    this.values[0] = value;
  }
}

const red = new Color(255, 0, 0);
red.setRed(0);
console.log(red.getRed()); // 0ããã¡ããããã®æ®µéã§ã¯ãé»ãã¨å¼ã°ãããã®ãªã®ã§ã

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ã¤ã³ã¹ã¿ã³ã¹ã® values éåã«ç´æ¥ã¢ã¯ã»ã¹ã§ããã®ã«ããããã getRed ã setRed ã¡ã½ãããä½¿ç¨ããå¿è¦ãããã®ããã¨æãããããããã¾ããã

class Color {
  constructor(r, g, b) {
    this.values = [r, g, b];
  }
}

const red = new Color(255, 0, 0);
red.values[0] = 0;
console.log(red.values[0]); // 0

class Color {
  constructor(r, g, b) {
    // values is now an HSL array!
    this.values = rgbToHSL([r, g, b]);
  }
  getRed() {
    return this.values[0];
  }
  setRed(value) {
    this.values[0] = value;
  }
}

const red = new Color(255, 0, 0);
console.log(red.values[0]); // 0ã255 ã§ã¯ãªããªãã¾ããç´ç²ãªèµ¤ã® H ã®å¤ã¯ 0 ã ããã§ãã

class Color {
  // å®£è¨: ããããã® Color ã¤ã³ã¹ã¿ã³ã¹ã«ã¯ã #values ã¨ãããã©ã¤ãã¼ããã£ã¼ã«ãããã
  #values;
  constructor(r, g, b) {
    this.#values = [r, g, b];
  }
  getRed() {
    return this.#values[0];
  }
  setRed(value) {
    this.#values[0] = value;
  }
}

const red = new Color(255, 0, 0);
console.log(red.getRed()); // 255

console.log(red.#values); // SyntaxError: Private field '#values' must be declared in an enclosing class

class Color {
  #values;
  constructor(r, g, b) {
    this.#values = [r, g, b];
  }
  getRed() {
    return this.#values[0];
  }
  setRed(value) {
    if (value < 0 || value > 255) {
      throw new RangeError("Invalid R value");
    }
    this.#values[0] = value;
  }
}

const red = new Color(255, 0, 0);
red.setRed(1000); // RangeError: Invalid R value

class Color {
  #values;
  constructor(r, g, b) {
    this.#values = [r, g, b];
  }
  redDifference(anotherColor) {
    // #values ã«ã¯ãå¿ãããããããã¢ã¯ã»ã¹ããå¿è¦ã¯ããã¾ããã
    // åãã¯ã©ã¹ã«å±ããä»ã®ã¤ã³ã¹ã¿ã³ã¹ã®ãã©ã¤ãã¼ããã£ã¼ã«ãã«
    // ã¢ã¯ã»ã¹ãããã¨ãã§ãã¾ãã
    return this.#values[0] - anotherColor.#values[0];
  }
}

const red = new Color(255, 0, 0);
const crimson = new Color(220, 20, 60);
red.redDifference(crimson); // 35

class Color {
  #values;
  constructor(r, g, b) {
    this.#values = [r, g, b];
  }
  redDifference(anotherColor) {
    if (!(#values in anotherColor)) {
      throw new TypeError("Color instance expected");
    }
    return this.#values[0] - anotherColor.#values[0];
  }
}

ã¡ã¢: ãã®ã¨ãã# ã¯ç¹æ®ãªèå¥åæ§æã§ããããã£ã¼ã«ãåãæååã®ããã«ä½¿ç¨ãããã¨ã¯ã§ããªããã¨ã«çæãã¦ãã ããã"#values" in anotherColor ã¯ããã©ã¤ãã¼ããã£ã¼ã«ãã§ã¯ãªããæåéã "#values" ã¨ããããããã£åãæ¢ãã¦ãããã¨ã«ãªãã¾ãã

class BadIdeas {
  #firstName;
  #firstName; // syntax error occurs here
  #lastName;
  constructor() {
    delete this.#lastName; // also a syntax error
  }
}

class Counter extends HTMLElement {
  #xValue = 0;
  constructor() {
    super();
    this.onclick = this.#clicked.bind(this);
  }
  get #x() {
    return this.#xValue;
  }
  set #x(value) {
    this.#xValue = value;
    window.requestAnimationFrame(this.#render.bind(this));
  }
  #clicked() {
    this.#x++;
  }
  #render() {
    this.textContent = this.#x.toString();
  }
  connectedCallback() {
    this.#render();
  }
}

customElements.define("num-counter", Counter);

ã¢ã¯ã»ãµã¼ãã£ã¼ã«ã

class Color {
  constructor(r, g, b) {
    this.values = [r, g, b];
  }
  get red() {
    return this.values[0];
  }
  set red(value) {
    this.values[0] = value;
  }
}

const red = new Color(255, 0, 0);
red.red = 0;
console.log(red.red); // 0

class Color {
  constructor(r, g, b) {
    this.values = [r, g, b];
  }
  get red() {
    return this.values[0];
  }
}

const red = new Color(255, 0, 0);
red.red = 0;
console.log(red.red); // 255

å³æ ¼ã¢ã¼ãã®å ´åãred.red = 0 ã®è¡ã¯ã"Cannot set property red of #<Color> which has only a getter" ã¨ããåã¨ã©ã¼ãçºçãã¾ããå³å¯ã¢ã¼ãä»¥å¤ã§ã¯ãä»£å¥ã¯æé»ã«ç¡è¦ããã¾ãã

ãããªãã¯ãã£ã¼ã«ã

class MyClass {
  luckyNumber = Math.random();
}
console.log(new MyClass().luckyNumber); // 0.5
console.log(new MyClass().luckyNumber); // 0.3

class MyClass {
  constructor() {
    this.luckyNumber = Math.random();
  }
}

éçããããã£

ã¡ã¢: ã¦ã¼ãã£ãªãã£ã¡ã½ããã®æ¥é è¾ã«ããã®ã¡ã½ãããæ±ããã®ãä»ãããã¨ã¯ãååç©ºéåãã¨å¼ã°ããè¯ãç¿æ£ã¨ããã¦ãã¾ããä¾ãã°ãJavaScript ã§ã¯ãå¤ãæ¥é è¾ã®ãªã parseInt() ã¡ã½ããã«å ããå¾ãããæ°åãæ±ãããã®ã¡ã½ããã§ãããã¨ãç¤ºãããã« Number.parseInt() ã¡ã½ãããè¿½å ããã¾ããã

éçã¡ã½ãã
éçãã£ã¼ã«ã
éçã²ãã¿ã¼ããã³ã»ãã¿ã¼

class Color {
  static isValid(r, g, b) {
    return r >= 0 && r <= 255 && g >= 0 && g <= 255 && b >= 0 && b <= 255;
  }
}

Color.isValid(255, 0, 0); // true
Color.isValid(1000, 0, 0); // false

ãã¹ã¦ã« static ã®æ¥é è¾ãä»ãã¦ããã
ã¤ã³ã¹ã¿ã³ã¹ããã¯ã¢ã¯ã»ã¹ã§ãã¾ããã

console.log(new Color(0, 0, 0).isValid); // undefined

class MyClass {
  static {
    MyClass.myStaticProperty = "foo";
  }
}

console.log(MyClass.myStaticProperty); // 'foo'

æ¡å¼µã¨ç¶æ¿

class Color {
  #values;
  constructor(r, g, b, a = 1) {
    this.#values = [r, g, b, a];
  }
  get alpha() {
    return this.#values[3];
  }
  set alpha(value) {
    if (value < 0 || value > 1) {
      throw new RangeError("Alpha value must be between 0 and 1");
    }
    this.#values[3] = value;
  }
}

class ColorWithAlpha extends Color {
  #alpha;
  constructor(r, g, b, a) {
    super(r, g, b);
    this.#alpha = a;
  }
  get alpha() {
    return this.#alpha;
  }
  set alpha(value) {
    if (value < 0 || value > 1) {
      throw new RangeError("Alpha value must be between 0 and 1");
    }
    this.#alpha = value;
  }
}

const color = new ColorWithAlpha(255, 0, 0, 0.5);
console.log(color.red); // 255

console.log(red.toString()); // [object Object]

class Color {
  #values;
  // â¦
  toString() {
    return this.#values.join(", ");
  }
}

console.log(new Color(255, 0, 0).toString()); // '255, 0, 0'

class ColorWithAlpha extends Color {
  #alpha;
  // â¦
  toString() {
    // è¦ªã¯ã©ã¹ã® toString() ãå¼ã³åºããè¿å¤ãæ§ç¯ãã
    return `${super.toString()}, ${this.#alpha}`;
  }
}

console.log(new ColorWithAlpha(255, 0, 0, 0.5).toString()); // '255, 0, 0, 0.5'

class ColorWithAlpha extends Color {
  // ...
  static isValid(r, g, b, a) {
    // è¦ªã¯ã©ã¹ã® isValid() ãå¼ã³åºããè¿å¤ã«ããã¦æ§ç¯ãã
    return super.isValid(r, g, b) && a >= 0 && a <= 1;
  }
}

console.log(ColorWithAlpha.isValid(255, 0, 0, -1)); // false

class ColorWithAlpha extends Color {
  log() {
    console.log(this.#values); // SyntaxError: Private field '#values' must be declared in an enclosing class
  }
}

const color = new ColorWithAlpha(255, 0, 0, 0.5);
console.log(color instanceof Color); // true
console.log(color instanceof ColorWithAlpha); // true

ãªãã¯ã©ã¹ã

function incrementDay(date) {
  return date.setDate(date.getDate() + 1);
}
const date = new Date(); // 2019-06-19
const newDay = incrementDay(date);
console.log(newDay); // 2019-06-20
// å¤ãæ¥ä»ãå¤ãã£ã¦ãã¾ãï¼ï¼
console.log(date); // 2019-06-20

function isRed(color) {
  return color.red === 255;
}
function isValidColor(color) {
  return (
    color.red >= 0 &&
    color.red <= 255 &&
    color.green >= 0 &&
    color.green <= 255 &&
    color.blue >= 0 &&
    color.blue <= 255
  );
}
// ...

Error ã¯ã©ã¹ã¯ãä¾å¤ã«é¢ããå·ä½çãªæå ±ãä¾ãã°ã¨ã©ã¼ã¡ãã»ã¼ã¸ãã¹ã¿ãã¯ãã¬ã¼ã¹ãåå ãªã©ãä¿æãã¾ããããã¯ãè±å¯ãªç¶æ¿æ§é ãæã¤ããã¤ãã®ã¯ã©ã¹ã® 1 ã¤ã§ããTypeError ã ReferenceError ãªã©ãError ãç¶æ¿ããè¤æ°ã®çµã¿è¾¼ã¿ã¯ã©ã¹ãããã¾ããã¨ã©ã¼ã®å ´åããã®ç¶æ¿ã«ãã£ã¦ã¨ã©ã¼ã®æå³ãçµãè¾¼ããã¨ãã§ãã¾ããããããã®ã¯ã©ã¹ãåºæã®ã¨ã©ã¼ã®ç¨®é¡ãè¡¨ãã®ã§ãinstanceof ã§å®¹æã«èª¿ã¹ããã¨ãã§ãã¾ãã

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Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://developer.mozilla.org/ja/docs/Web/JavaScript/Guide/Using_classes below:

ã¯ã©ã¹ã®ä½¿ç¨ - JavaScript | MDN

ã¯ã©ã¹ã®ä½¿ç¨ - JavaScript | MDN