I'm using model classes that extend a base Model class. The Model class returns a Proxy from the constructor that allows me to access properties passed into the constructor without having to explicitly define them on the class.
Using this, I can access a property of the data object externally, but attempting to access it internally returns undefined. How can I access the proxied properties from within the class itself?
class Model {
constructor(data) {
this.data = data;
return new Proxy(this, {
get(model, prop) {
if (model.hasOwnProperty(prop) || prop in model) {
return model[prop];
}
if (model.data.hasOwnProperty(prop)) {
return model.data[prop];
}
}
});
}
}
class User extends Model {
get name() {
return `${this.first_name} ${this.last_name}`;
}
}
const user = new User({
first_name: 'Bob',
last_name: 'Smith'
});
console.log(user.first_name); // 'Bob'
console.log(user.name); // undefined undefinedYou need to use Reflect.get() to access properties on the original object
Reflect
Reflect is a built-in object that provides methods for interceptable JavaScript operations. The methods are the same as those of proxy handlers. Reflect is not a function object, so it's not constructible.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect
Reflect.get()
The static
Reflect.get()method works like getting a property from an object (target[propertyKey]) as a function.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect/get
class Model {
constructor(data) {
this.data = data
return new Proxy(this, {
get(model, prop) {
if (model.data.hasOwnProperty(prop)) {
return model.data[prop]
}
return Reflect.get(...arguments)
},
})
}
}
class User extends Model {
get name() {
return `${this.first_name} ${this.last_name}`
}
}
const user = new User({
first_name: 'Bob',
last_name: 'Smith',
})
console.log(user.first_name) // 'Bob'
console.log(user.name) // 'Bob Smith'Reflect.get takes 3 arguments: the object, the key, and and optional this context.
Here Reflect.get(...arguments) is equivalent to Reflect.get(model, prop)
Reflect.getReflect.get({ x: 1, y: 2 }, 'x') // 1
Reflect.get(['zero', 'one'], 1) // "one"