Typescript JSON to Class with "es5"

Question

What is the best/common way to cast a JSON into a class in Typescript with ES5 (no Object.assign()).

e.g.

export class Lesson{
 name:string;
 teacher:Teacher;
 date:Date;
 scholars:Array<string>; //or string[] ... I dont care
}

The JSON would look like:

{
 name:"LessonName",
 teacher:{name:"masterT", age:120},
 date:12345678912
 scholars:["Jim","Bob","Jimbo"]
}

In Typescript I can cast the JSON to a Object and even assign it straight to a Lesson object (!-horrible behaviour, but thats JS-!)

But the object don't have any methods for example.

e.g. So lesson.date.getTime() won't work.

So how to handle that correctly?

Possible duplicate of [How do I initialize a typescript object with a JSON object](https://stackoverflow.com/questions/22885995/how-do-i-initialize-a-typescript-object-with-a-json-object) — jcalz, Sep 01 '17 at 17:27
This is the job for the `constructor` of a class. This way you can cast the date field into a Date object etc so you can do `new Lesson(attributes)` — Fotis, Sep 01 '17 at 17:28

Christof Hullaert · Answer 1 · 2017-09-01T17:23:29.453

0

Try

// first declare variable
var lesson: Lesson;

// and then assign that
lesson={
 name:"LessonName",
 teacher:{name:"masterT", age:120},
 date:12345678912
 scholars:["Jim","Bob","Jimbo"]
}

But the problem is that you want to put only a value in an object.

edited Sep 01 '17 at 17:23

answered Sep 01 '17 at 17:04

Christof Hullaert

311
3
12

This is not valid TypeScript, nor does it answer the question properly (for instance, the `date` property is not a `Date` object.) – jcalz Sep 01 '17 at 17:20
But `lesson` is still not an instance of the `Lesson` class. You need to do something like `lesson = new Lesson()`, and then start setting properties. And `date` is still not a `Date`. Sorry, but this is not a proper answer. – jcalz Sep 01 '17 at 17:25
you can also see there, same problem. – Christof Hullaert Sep 01 '17 at 17:25
https://stackoverflow.com/questions/40421100/how-to-parse-a-json-object-to-a-typescript-object – Christof Hullaert Sep 01 '17 at 17:25
You can also use this library https://www.npmjs.com/package/serializer.ts – Christof Hullaert Sep 01 '17 at 17:27
Yeah, it seem I cant avoid manual code here. -Again: Object.assign() ist not available. Nor it helps lot with encapsuled classes. – Gregor Sklorz Sep 04 '17 at 11:17

Typescript JSON to Class with "es5"

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