Elegant way to copy only a part of an object [duplicate]

Answer 1

You can do it like below via Spread Operator

let source = {
    x: 120,
    y: 200,
    z: 150,
    radius: 10,
    color: 'red',
};

let {radius, color, ...newObj} = source;
console.log(newObj);

Answer 2

For simple cases like this the object destructuring mentioned in other answers is very neat but tends to look a bit cumbersome when dealing with larger structures as you double up on property names.

Expanding on your own answer - if you were going to write an extract utility (I'll roll my own for fun)... you can make it more flexible by currying it - allowing you to swap the order of the arguments (notably putting the data source last) while still being variadic in accepting property names.

I'd consider this signature: extract = (...props) => src => { ... } more elegant as it allows for a greater degree of reuse in composing new, named functions:

const extract = (...props) => src => 
    Object.entries(src).reduce(
        (obj, [key, val]) => (
            props.includes(key) && (obj[key] = val), 
            obj
    ), {})

const getCoords = extract('x', 'y', 'z')

const source = {
    x: 120,
    y: 200,
    z: 150,
    radius: 10,
    color: 'red'
}

console.log(getCoords(source))

Answer 3

One way to do it is through object destructuring and an arrow function:

let source = {
    x: 120,
    y: 200,
    z: 150,
    radius: 10,
    color: 'red',
};

let result = (({ x, y, z }) => ({ x, y, z }))(source);

console.log(result);

The way this works is that the arrow function (({ x, y, z }) => ({ x, y, z })) is immediately called with source as the parameter. It destructures source into x, y, and z, and then immediately returns those as a new object.

Answer 4

IIFE with destructuring maybe?:

const coords = (({x, y, z}) => ({x, y, z}))(source);

Answer 5

Just take a function.

const extract = ({ x, y, z }) => ({ x, y, z });

let source = { x: 120, y: 200, z: 150, radius: 10, color: 'red' };

console.log(extract(source));

Another solution is a destructuring to a target object with target properties.

let source = { x: 120, y: 200, z: 150, radius: 10, color: 'red' }, 
    target = {};

({ x: target.x, y: target.y, z: target.z } = source);

console.log(target);

Answer 6

1st method is elegant and readable.

Please don't obfuscate simple operations by some workarounds. Other people who will need to maintain this code, including future yourself will be very thankful in the future.