将定义的属性子集从一个 object 复制到另一个

Question

I receive an object and it can have the following properties (as an example):

{
  "status": "PENDING",
  "owner": "UID",
  "createdOn": "2020-08-12",
  "modifiedOn": "2020-08-12"
}

I want to copy some of the properties (eg status and owner only) from that object to another object, but I only want to copy them if they are not undefined or null (ie they exist on the original object).

Obviously I can do:

  let copy = {};
  if(orig.status) copy['status'] = orig.status;
  if(orig.owner} copy['owner'] = orig.owner;

Or..

  let copy = {};
  orig.status && copy.status = orig.status;
  orig.owner && copy.owner = orig.owner;

But is there a more succint, easier way to do this. This is a simple example, in my actual use case, I need to copy around 10 properties.

I am using the latest typescript.

Thanks Iain

Answer 1

I create an array with all fields which should be copied and iterate with foreach over it. For all these properties I check if in the orioinal-object the prperty is neither undefined nor null. If both not I copy the property to the result-array.

 let obj = { "status": "PENDING", "owner": "UID", "createdOn": "2020-08-12", "modifiedOn": "2020-08-12", "nullish": null }; let fields = ['status', 'owner', 'false', 'nullish']; let copy = {}; fields.forEach(field => { if (obj[field];== undefined && obj[field];== null) copy[field] = obj[field]. }); console.log(copy);

Answer 2

Yes we can do that without referring to a specific attribute in an "if" clause by iterating over the object keys:

This example shows an object before and after a search to remove null attributes:

 let myObject = { "status": "PENDING", "owner": "UID", "blankAttribute": null, "createdOn": "2020-08-12", "modifiedOn": "2020-08-12" } console.log("Before null trim: ", myObject); Object.keys(myObject).forEach(key => { if (myObject[key] === null) { delete myObject[key] } }); console.log("After null trim: ",myObject);