是否存在与goog.object.extend等效的纯函数？

Question

Per Closure documentation :

Extends an object with another object. This operates 'in-place'; it does not create a new Object. Example: var o = {}; goog.object.extend(o, {a: 0, b: 1}); o; // {a: 0, b: 1} goog.object.extend(o, {b: 2, c: 3}); o; // {a: 0, b: 2, c: 3}

But this is not a functional approach and for many contexts a functional approach is better. Does Closure offer something more modern for this?

eg

goog.object.extend(a, b);

becomes

a = goog.object.extend(a, b);

Answer 1

You can create a new object by using an empty object literal to be extended with the objects that you want to copy-merge:

var x = {};
goog.object.extend(x, a, b);
a = x;

If you are extending non-plain objects, you might need to use Object.create(Object.getPrototypeOf(a)) .

Answer 2

You could implement it yourself:

 var a = {}; var b = extend(a, { a: 0, b: 1 }); var c = extend(b, { b: 2, c: 3 }); console.log(a, b, c); function extend(a, b) { var result = {}; for (var x in a) if (a.hasOwnProperty(x)) result[x] = a[x]; for (var x in b) if (b.hasOwnProperty(x)) result[x] = b[x]; return result; } 

Hope that helps.