Is there a pure functional equivalent to goog.obje

问题:

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?

e.g.

goog.object.extend(a, b);

becomes

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

回答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)).

回答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.