Deep cloning Entity instances in Typescript?

If you duplicate an object with the spread operator, your new object won't be an instance of a class, but a literal object with no type, so it won't be a real clone of the existing object.

If the objects you want to clone are defined by you (not an external library) you could do something like:

export function deepClone(array: any[]): any[] {  return array.map((e:any) => (new e.constructor(e)));}

And then in your classes meant to be cloned:

constructor(obj: any) {   Object.assign(this, obj);}

I use this method

https://stackblitz.com/edit/typescript-qmzgf7

const clone = obj =>  Array.isArray(obj)    ? obj.map(item => clone(item))    : obj instanceof Date      ? new Date(obj.getTime())      : (typeof obj === 'object') && obj        ? Object.getOwnPropertyNames(obj).reduce((o, prop) => ({ ...o, [prop]: clone(obj[prop]) }), {})        : obj;

It doesn't work for all JavaScript object you might encounter, but it will likely work for anything that comes from a server call in JSON format.

In regards to your actual implementation, you should consider using old mate JSON to help you out with this.

var array:Array<number> = [1,2,3];var deepClone = clone(array);deepClone[0] = 99;console.log({ array, deepClone });  // returns [1,2,3] & [99,2,3]function clone<T>(array:T[]) {return JSON.parse(JSON.stringify(array)) as Array<T>;}