JavaScript: Object.defineProperties

Object.defineProperties( obj, {key1: descriptor1}, {key2: descriptor2} etc)

Create properties or modify existing properties.
Return the modified obj.
The descriptor1, descriptor2, etc are Property Descriptor.

To create/modify only 1 property, use Object.defineProperty

const yy = {};

// add 2 properties, with their attributes
Object.defineProperties(
yy,
{
x1:{ value : 1, writable: true, enumerable: true, configurable: true},
x2:{ value : 2, writable: true, enumerable: true, configurable: true}
}
);

console.log(yy); // { x1: 1, x2: 2 }