如何使用扩展语法从 JavaScript 中的多个未知对象复制 object 属性？

Question

I would like to use spread syntax to copy properties from several unknown objects into one object. Something like this:

var array = [{a:0}, {b:1}, {c:2}]; // This array could hold any number of objects

// This function should take the objects in the array and use spread syntax to create a new object.
function merge(arr) { /* Code I wish I knew */ } // returns an object

var combo = merge(array);

console.log(combo); // {a:0, b:1, c:2}

I am aware of Object.assign . My reason for asking this question is just to see if this sort of thing can be done with spread syntax. Additionally, I'm concerned with V8's Hidden Classes. From what I understand, modifying an object after it is instantiated negatively impacts the performance of the Hidden Class. I've read that Spread doesn't have this issue, possibly because it instantiates the object with all of the properties of the other objects.

Answer 1

You can use a combination of Array.reduce with Object.assign :

 var array = [{a:0}, {b:1}, {c:2}]; function merge(arr) { return array.reduce((x,y) => Object.assign(x, y)) // // per the comments, if we don't want to mutate the original object we can do instead: // return array.reduce((x,y) => Object.assign(x, y), {}) } var combo = merge(array); console.log(combo);

Answer 2

You can use Array#reduce to iterate the array and merge the children into one object:

 var array = [{a:0}, {b:1}, {c:2}]; function merge(arr) { return arr.reduce((acc, cur) => ({...acc, ...cur })); } var combo = merge(array); console.log(combo);