javascriptecmascript-6ecmascript-harmonydestructuringecmascript-next

One-liner to take some properties from object in ES 6


How one can write a function, which takes only few attributes in most-compact way in ES6?

I've came up with solution using destructuring + simplified object literal, but I don't like that list of fields is repeated in the code.

Is there an even slimmer solution?

(v) => {
    let { id, title } = v;
    return { id, title };
}

Solution

  • Here's something slimmer, although it doesn't avoid repeating the list of fields. It uses "parameter destructuring" to avoid the need for the v parameter.

    ({id, title}) => ({id, title})
    

    (See a runnable example in this other answer).

    @EthanBrown's solution is more general. Here is a more idiomatic version of it which uses Object.assign, and computed properties (the [p] part):

    function pick(o, ...props) {
        return Object.assign({}, ...props.map(prop => ({[prop]: o[prop]})));
    }
    

    If we want to preserve the properties' attributes, such as configurable and getters and setters, while also omitting non-enumerable properties, then:

    function pick(o, ...props) {
        var has = p => o.propertyIsEnumerable(p),
            get = p => Object.getOwnPropertyDescriptor(o, p);
    
        return Object.defineProperties({},
            Object.assign({}, ...props
                .filter(prop => has(prop))
                .map(prop => ({prop: get(props)})))
        );
    }