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21.getters and setters.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
You can obtain values from an object and set the value of a property within an object.
These are classically called getters and setters.
<script>
// Getter functions are meant to simply return (get) the value of an object's private variable to the user without the user directly accessing the private variable
// Getter函数意味着简单地向用户返回(get)对象私有变量的值，而不需要用户直接访问私有变量
// Setter functions are meant to modify (set) the value of an object's private variable based on the value passed into the setter function.
// Setter函数意味着根据传入Setter函数的值修改(设置)对象的私有变量的值。
// This change could involve calculations, or even overwriting the previous value completely.
class Book {
constructor(author) {
this._author = author;
}
//getter
get writer() {
return this._author;
}
//setter
set writer(updateAuthor) {
this._author = updateAuthor;
}
}
// 闭包实现get和set
;(function(){
var _secret = 0;
getValue = function () {
return _secret;
};
setValue = function(U){
_secret = U;
}
})()
// 调用
getValue();
setValue(3);
getValue();
// 对比闭包
// 对比闭包
// 对比闭包
// 对比闭包
// 对比闭包
// 对比闭包
// 对比闭包访问私有变量
const lol = new Book('ano');
console.log(lol.writer);
lol.writer = 'wut';
console.log(lol.writer);
// invoke 调用
// Getters and setters are important because they hide internal implementation details
// precede 提前
/*
It is convention to precede the name of a private variable with an underscore (_). However, the practice itself does not make a variable private.
按照惯例，在私有变量名之前加上下划线(_)。然而，实践本身并没有将变量设为私有。
*/
/*
This is the power of a getter and a setter. You are creating an API for another user, who can get the correct result regardless of which one you track.
In other words, you are abstracting implementation details from the user.
这就是getter和setter的威力。您正在为另一个用户创建一个API，无论您跟踪哪个用户，该用户都可以获得正确的结果。
换句话说，您正在从用户抽象实现细节。 */
/* Alter code below this line */
class Thermostat {
constructor(Fahrenheit) {
this._Fahrenheit = Fahrenheit;
}
get temperature() {
return (this._Fahrenheit - 32) * 5 / 9;
}
set temperature(update) {
this._Fahrenheit = (update * 9) / 5 + 32;
}
}
/* Alter code above this line */
const thermos = new Thermostat(76); // setting in Fahrenheit scale
let temp = thermos.temperature; // 24.44 in C
thermos.temperature = 26;
temp = thermos.temperature; // 26 in C
</script>
</body>
</html>