Preserving original properties in Typecript object class

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How do I preserve the original properties of a class object when mapping with the new object.

Let's say I have a class with the following property.

export class User{
 public name: string;
 public age: number;
 public internalId: number;

Following is where I am assigning values from call back subscribe() function

                if(data && data.length > 0){
                    this.User = data;

Now the data I receive from service only contains a name and age. Not internalId property.

After assigning via subscribe function, I only left with name and age.

I don't really know if this question was answered before or at least I don't really know what the right way to ask.

With Object.assign.

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

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You can use Object.assign to copy all properties from your returned object into an actual User object.

I recommend using RxJS' map operator before subscribing:

  map(data => Object.assign(new User(), data))
).subscribe((user: User) => {
  this.User = user;

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You can also use lodash merge to deal with complex entities:

var object = {
  'a': [{ 'b': 2 }, { 'd': 4 }]

var other = {
  'a': [{ 'c': 3 }, { 'e': 5 }]

_.merge(object, other);
// => { 'a': [{ 'b': 2, 'c': 3 }, { 'd': 4, 'e': 5 }] }

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Replace this.User = data; with this.User = {...this.User,};

  data => {
    if (data) {
      this.User = { ...this.User, };

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How do I preserve typing information through indexed properties types, Keeping Our Properties Private In fact, all properties in TypeScript classes are public by default. worked with properties and methods that belong to the instance, meaning the object that is created by the constructor. On Medium, smart voices and original ideas take center stage - with no ads in sight. Describes a technique of how a TypeScript class property can be made "virtualized" so that when the property is used in certain context, the context will reflect the latest value assigned to the

Write Beautiful OO Classes with TypeScript, Copying all properties of one object to another one is a common operation in JavaScript. and TypeScript both have ways of doing this, but I prefer this syntax ): class Point class Point { constructor(x, y) { Object.assign(this, { x, y }); } } If it was a "copy" how can its modification change the original object? Object is basically instance of class, by using object we can assess all the available properties, functions of a class. Object is an Instance of class So let’s say you have class called a User and it has method likes profile so to call the profile method of that particular user class you have to use object.

ECMAScript 6: merging objects via Object.assign(), ISRO CS Solved Papers � ISRO CS Original Papers and Official Keys � ISRO CS Syllabus for Scientist/Engineer Exam. UGC NET Class(constructor) objects: A class object is an instance of a Typescript class with own defined properties, constructors and methods. Todo class object Storing the new class. JavaScript provides a bunch of good ways to access object properties. The dot property accessor syntax works nicely when you know the variable ahead of time. When the property name is dynamic or is not a valid identifier, a better alternative is square brackets property accessor: object[propertyName].

  • Which I will assign later, maybe numbers. 1st I load this data, then render HTML elements, based on users interaction with each set of the object I will flag the internalId. which then be processed for submission based on this flag.
  • So what does this pipe do?
  • pipe is how you apply RxJS operators to your observables. See
  • Still, it over writes the original class properties.
  • Not sure to follow. Can you maybe create a StackBlitz to reproduce the issue?
  • I mean, what I want is after observable call, I should see the original property internalId so that I can later use it for submition back to API. if this property is not there, I cannot actually submit since this will throw property not found exception.
  • I removed the check data.length > 0 because an object does not have length property.