Is it possible to do object initialization in JavaScript similar to C#?

Question

More specifically, for a random class with two public properties, in C# you can do something like this :

new Point() {
   Y = 0,
   X = 0
}

Is it possible to do something similar in JavaScript? I was thinking of something along the line of :

{
   prototype : Object.create(Point.prototype),
   X : 0,
   Y : 0
}

but I don't think it works as intended. Or a simple copy function :

function Create(object, properties) {
    for (p in properties)
        object[p] = properties[p];

    return object;
}

so the object initialization would become :

Create(new Point(), {X : 0, Y : 0});

but there is an extra object creation. Is there a better way of achieving this?

What are you trying to achieve (in terms of functionality)? Javascript is not C#. — Lekensteyn
– Lekensteyn, Commented Jan 20, 2012 at 20:24
Copying the prototype of Point into a new object, while initializing different properties of that object. — Colin Dumitru
– Colin Dumitru, Commented Jan 20, 2012 at 20:27

Konrad Korus · Accepted Answer · 2018-10-25 21:48:50Z

3

Using ES7:

class Point {
  x = 0;
  y = 0;
}

// {x: 5, y: 10}
const p = {...new Point(),  x: 5, y: 10 };

https://codepen.io/anon/pen/WaLLzJ

answered Oct 25, 2018 at 21:48

Konrad Korus

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1 Comment

Jean-Baptiste Martin Over a year ago

This solution shouldn't be used since the Point prototype is lost when using spread operator.

Rehmat · Accepted Answer · 2019-08-15 07:24:26Z

2

For those who code in TypeScript, here is another way to do it:

Create a base class:

export class BaseClass<T> {
    constructor(data?: Partial<T>) {
        Object.assign(this, data);
    }
}

Extend it:

import { BaseClass } from './base.model';

export class Child extends BaseClass<Child > {
    Id: string;
    Label: string;
}

Then you can do something like this:

const child = new Child({
    Id: 1,
    Label: 'My Label'
});

edited Aug 15, 2019 at 7:24

Rehmat

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answered Aug 15, 2019 at 6:56

Giang Phạm

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1 Comment

B--rian Over a year ago

Welcome to SO! Could you please edit your question and explain a bit more what you are doing, i.e. why your solution works.

Raynos · Accepted Answer · 2012-01-20 20:24:50Z

1

var Point = { /* methods */ };

Object.create(Point, {
    x: { value: 0 },
    y: { value: 0 }
});

Of course that's a bit verbose on the default property initialization so I tend to use an extend utility.

extend(Object.create(Point), {
    x: 0,
    y: 0
});

answered Jan 20, 2012 at 20:24

Raynos

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Comments

Darin Dimitrov · Accepted Answer · 2012-01-20 20:24:45Z

1

Object literals are probably the closest:

var point = {
    X: 0,
    Y: 0
};

answered Jan 20, 2012 at 20:24

Darin Dimitrov

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1 Comment

Colin Dumitru Over a year ago

But this method does not copy the prototype of Point. That is the dilemma.

Esailija · Accepted Answer · 2012-01-20 20:33:59Z

0

Nothing general (that meets your requirements) but you could do this:

function Point( x, y ) {
    this.x = x || 0;
    this.y = y || 0;
}

Point.prototype = { ... };

new Point( 1,2 );

answered Jan 20, 2012 at 20:33

Esailija

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