[英]JavaScript: Create Function that returns a function that returns output with getter / setter capabilities
I am trying to create a function that has setter and getter capabilities. 我正在尝试创建一个具有setter和getter功能的函数。
Below are my test specs. 以下是我的测试规格。
it('the returned function can get properties of the given object', () => {
let accessObject = accessor({ a: 100 });
expect(accessObject('a')).toEqual(100);
accessObject = accessor({ foobar: [7, 8, 9] });
expect(accessObject('foobar')).toEqual([7, 8, 9]);
expect(accessObject('a')).toEqual(undefined);
});
it('the returned function can set properties of the given object', () => {
const obj = { stuff: 'something' };
const accessObject = accessor(obj);
accessObject('stuff', 'a new value');
expect(obj.stuff).toEqual('a new value');
expect(obj['pizz-pie']).toEqual(undefined);
// key value
accessObject('pizza-pie', 'yummmm');
expect(obj['pizza-pie']).toEqual('yummmm');
});
});
The code below passes my test specs but I am confused by why, specifically on the setter portion of my code. 下面的代码通过了我的测试规范,但是我对为什么感到困惑,尤其是在代码的设置部分。
const accessor = obj => {
return (prop, value) => {
if (value === undefined) {
return obj[prop];
} else {
// QUESTION: what is going on here?
return obj[prop] = value;
}
};
};
Please see my question commented in my code above. 请在上面的代码中查看我的问题。
Without a value
passed as a parameter, then your code acts like a getter. 如果没有将value
作为参数传递,那么您的代码就像一个吸气剂。 Otherwise, it acts as a setter buy returning the property value immediate after setting it. 否则,它充当设置器购买者,在设置后立即返回属性值。
You can think of this being written this way alternatively; 您可以想到这种替代方式;
if (value === undefined) {
return obj[prop];
} else {
obj[prop] = value;
return obj[prop];
}
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