# obj.mergeWith()

[JS](https://lochiwei.gitbook.io/web/js) ⟩ [object](https://lochiwei.gitbook.io/web/js/val/obj) ⟩ [built-in](https://lochiwei.gitbook.io/web/js/val/builtin) ⟩ [Object](https://lochiwei.gitbook.io/web/js/val/builtin/object) ⟩ [extension](https://lochiwei.gitbook.io/web/js/val/builtin/object/ext) ⟩ obj.mergeWith(...sources)

{% tabs %}
{% tab title="💾 程式" %}

* replit ⟩ [obj.mergeWith(...sources)](https://replit.com/@pegasusroe/objmergeWithsources#ext/Object_ext.js), compare with [.assigndescriptors](https://lochiwei.gitbook.io/web/js/val/obj/extend/mixin/.assigndescriptors "mention")
* require [](https://lochiwei.gitbook.io/web/js/val/builtin/object/ext "mention")

```javascript
Object.defineProperties(Object.prototype, {

    // 🔹 other related methods omitted ...
    
    // 🔹 obj.mergeWith(...sources)
    mergeWith: {
        value: function(...sources) {

            const descriptors = {};
            
            // collect all descriptors from sources
            sources.forEach(source => {
                
                // own enumerable (string-keyed) properties -> descriptors
                source.keys.forEach(key => {
                    descriptors[key] = source.propertyDescriptor(key);
                });
        
                // own enumerable (symbol-keyed) properties -> descriptors
                source.symbols.forEach(sym => {
                    const desc = source.propertyDescriptor(sym);
                    if (desc.enumerable) descriptors[sym] = desc;
                });
        
            });
        
            // merge
            return this.defineProperties(descriptors);
        },
    },

});
```

{% endtab %}

{% tab title="💈範例" %}

* [replit](https://replit.com/@pegasusroe/objmergeWithsources#index.js), require [](https://lochiwei.gitbook.io/web/js/val/builtin/object/ext "mention")

```javascript
const source = {
  x: 1,                  // data property
  get y() { return 2 },  // accessor (getter)
};

({}).assign(source)      // { x: 1, y: 2 }
({}).mergeWith(source)   // { x: 1, y: [Getter] }
```

{% endtab %}

{% tab title="👥 相關" %}

* compare with [object.assign](https://lochiwei.gitbook.io/web/js/val/obj/extend/object.assign "mention")
* [extend](https://lochiwei.gitbook.io/web/js/val/obj/extend "mention")
* this method needs to [enumerate](https://lochiwei.gitbook.io/web/js/val/obj/prop/enumerate "mention") and deal with their [attr](https://lochiwei.gitbook.io/web/js/val/obj/prop/attr "mention")(s).
  {% endtab %}

{% tab title="📘 手冊" %}

* [Object.assign()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign) ⟩ [copying accessors](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign#copying_accessors)
  {% endtab %}
  {% endtabs %}


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