用期望的属性填充Javascript中的对象

Question

I have a prototype

class Animal() {
    constructor(name, weight) {
        this.name = name
        this.weight = weight
    }
}

and some coming object, which contains these properties plus something else

const obj = {
    name: "name",
    weight: 5,
    someRedundantProp: "bla"
}

I really enjoy JS mapping with Object.assign which would generically create an object for me with all properties, but here I want to fill this new object only with essential fields. Surely, I can map this object like

new Animal(obj.name, obj.weight)

but if at some point I would introduce new properties I will have to change code here, what I don't want to.

Is there some better way?

Answer 1

This should work for you:

class Animal {
    constructor(obj) {
        const defaultFields = {
            name: "",
            weight: 0
        }
        Object.keys(defaultFields).forEach(key => defaultFields[key] = obj[key]);
        Object.assign(this, defaultFields);
    }
}

Answer 2

You could check if the first argument is an object and then assign the object to this.

But be warned, this has some nasty side effects too.

 class Animal { constructor( obj ) { // Create an object that holds all available options const defaultOptions = { name: '', weight: 0, }; // Go over all available options Object.keys( defaultOptions ).forEach( key => { // Check if obj has key, otherwise use default option this[ key ] = obj[ key ] || defaultOptions[ key ]; } ); } } const obj = { name: "name", weight: 5, someRedundantProp: "bla" } const a = new Animal( obj ); console.log( a ); 

Answer 3

I came to this solution for now

let animal = new Animal()
Object.keys(animal).forEach(field => animal[field] = obj[field])