爲何使用Getter和Setter?Getter和Setter有什麼區別?

JavaScript訪問器(Getter和Setter),ECMAScript 5(2009)介紹了Getter和Setters。 Getters和setter容許您定義對象訪問器(Computed Properties)。javascript

JavaScript Getter(get關鍵字)

<!DOCTYPE html>
<html>
<meta charset="utf-8">
<title>js</title>
<body>

<h2>JavaScript Getters和Setters</h2>

<p> Getters和setter容許您經過方法獲取和設置屬性。</p>

<p>此示例使用lang屬性獲取語言屬性的值。</p>

<p id="demo"></p>

<script>
    // 新建一個對象。
    var person = {
        firstName: "John",
        lastName : "Doe",
        language : "en",
        get lang() {
            return this.language;
        }
    };
    // 使用getter顯示來自對象的數據:
    document.getElementById("demo").innerHTML = person.lang;
</script>

</body>
</html>

JavaScript Setter (set關鍵字)

<!DOCTYPE html>
<html>
<meta charset="utf-8">
<title>JavaScript Getters和Setters</title>
<body>

<h2> JavaScript Getters和Setters </h2>

<p> Getters和setter容許您經過方法獲取和設置屬性。</p>

<p>此示例使用lang屬性設置語言屬性的值。</p>

<p id="demo"></p>

<script>
    // Create an object:
    var person = {
        firstName: "John",
        lastName : "Doe",
        language : "NO",
        set lang(value) {
            this.language = value;
        }
    };
    // Set a property using set:
    person.lang = "en";
    // Display data from the object:
    document.getElementById("demo").innerHTML = person.language;
</script>

</body>
</html>

爲何使用Getter和Setter?

  • 它提供了更簡單的語法
  • 它容許屬性和方法的語法相同
  • 它能夠確保更好的數據質量
  • 在幕後作事情頗有用
<!DOCTYPE html>
<html>
<meta charset="utf-8">
<title>js</title>
<body>

<h2> JavaScript Getters和Setters </h2>

<p>完美的建立反對象:</p>

<p id="demo"></p>

<script>
    var obj = {
        counter : 0,
        get reset() {
            this.counter = 0;
        },
        get increment() {
            this.counter++;
        },
        get decrement() {
            this.counter--;
        },
        set add(value) {
            this.counter += value;
        },
        set subtract(value) {
            this.counter -= value;
        }
    };
    // Play with the counter:
    obj.reset;
    obj.add = 5;
    obj.subtract = 1;
    obj.increment;
    obj.decrement;
    // Display the counter:
    document.getElementById("demo").innerHTML = obj.counter;
</script>

</body>
</html>

Object.defineProperty()方法還可用於添加Getters和Setterhtml

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