Javascript 将Singleton实例设置为未定义后的Angular 变量引用持久性行为

// Create the first instance.
let obj = { foo: 'bar' };

// Capture a reference to the first instance.
const a = obj;

// Forget the reference to the first instance.
// NOTE: this does not destroy the first instance,
// it just removes obj's reference to the first
// instance.
obj = undefined;

// Create the second instance.
obj = { foo: 'baz' };

// Capture a reference to the second instance.
const b = obj;

// Log the instances (Prints 'bar' and 'baz' respectively). 
console.log(a.foo);
console.log(b.foo);

// Create the first instance.
let obj = { foo: 'bar' };

// Capture a reference to the first instance.
const a = obj;

// Update a property on the first instance.
obj.foo = 'baz';

// Capture a second reference to the first instance.
const b = obj;

// Log the instances (Prints 'bar' and 'baz' respectively). 
console.log(a.foo);
console.log(b.foo);

class SingletonClass {

    static #instance;
    name;
    
    static getInstance() {
        if (SingletonClass.#instance == undefined)
            SingletonClass.#instance = new SingletonClass();
        
        return SingletonClass.#instance;
    }

    static destroy() {
        SingletonClass.#instance = undefined;
    }
}

// This has to be 'let' now since we're going
// to be reassigning our reference to point to the
// new instance.
let a = SingletonClass.getInstance();
a.name = 'Foo';

SingletonClass.destroy();

// We know we've destroyed the first instance so we
// should update our stored references to point to
// the new instance instead.
a = SingletonClass.getInstance();

const b = SingletonClass.getInstance();
b.name = 'Bar';

console.log(a.name);
console.log(b.name);

class SingletonClass {

    static #instance;
    name;
    
    static getInstance() {
        if (SingletonClass.#instance == undefined)
            SingletonClass.#instance = new SingletonClass();
        
        return SingletonClass.#instance;
    }

    static destroy() {
        SingletonClass.#instance = undefined;
    }
}

const a = () => SingletonClass.getInstance();
a().name = 'Foo';

SingletonClass.destroy();

const b = () => SingletonClass.getInstance();
b().name = 'Bar';

console.log(a().name);
console.log(b().name);