Angular typescript object.assign 不工作（它 return 错误无法读取 'length' of null）

Question

在文件“a.ts”，它将调用文件“b.ts”

的 handleRequests()

_alerts: Banner[];
obj = {};

postMessage() {
   this.obj[this._alerts[0].uuid] = this._alerts;
   const data = {
        'object': this.obj
   };
   this.service.handleRequests(stateAction);
}
postMessage();

在文件“b.ts”，

I would like to combine "data.object" with "this.object" and store the result at "this.object" variable. 

When initialize object to null, at run time it gives "TypeError: Cannot read property 'length' of null"

object = null ;
handleRequests(data) {
   this.object = Object.assign({}, ...this.object, ...data.object);
}

If intialize object to {}, at compile time it gives error "type { } is not an array type."

object = {}
handleRequests(data) {
   this.object = Object.assign({}, ...this.object, ...data.object);
}

“b.ts”处的对象初始化是否存在一些问题？

Answer 1

从您的 Object.assign 调用中删除扩展运算符 (...)，如下所示：

object = null;
handleRequests(data) {
   this.object = Object.assign({}, this.object, data.object);
}

或者，使用扩展运算符代替 Object.assign:

object = {};
handleRequests(data) {
   this.object = { ...this.object, ...data.object };
}

这是实现相同效果的两种不同方式。选择一个，而不是两个。另请注意，您不能在 null.

的对象上使用第二种方法（展开）

Angular typescript object.assign 不工作（它 return 错误无法读取 'length' of null）

Angular typescript object.assign not working (it return error cannot read 'length' of null)

javascript

typescript

ecmascript-6

angular8

deep-copy