combine

Core/combine.js 35
Merges two objects, copying their properties onto a new combined object. When two objects have the same property, the value of the property on the first object is used. If either object is undefined, it will be treated as an empty object.
Example:
const object1 = {
    propOne : 1,
    propTwo : {
        value1 : 10
    }
}
const object2 = {
    propTwo : 2
}
const final = Cesium.combine(object1, object2);

// final === {
//     propOne : 1,
//     propTwo : {
//         value1 : 10
//     }
// }