How to dynamically assign value to class property in TypeScript

Question

I would like to dynamically assign multiple properties to MyClass in TypeScript so there is no need to write multiple lines of code for setting class properties. I wrote the following code:

interface IMy
{
    visible?: boolean;
    text?: string;
}

class MyClass
{
    element: JQuery;

    assing(o: IMy): void
    {
        for (let [key, value] of Object.entries(o))
        {
            if (typeof value !== "undefined")
                this[key] = value;
        }
    }

    get visible(): boolean
    {
        return this.element.is(":visible");
    }

    set visible(visible: boolean)
    {
        this.element.css("display", visible ? "" : "none");
    }

    get text(): string
    {
        return this.element.html();
    }

    set text(text: string)
    {
        this.element.html(text);
    }
}

let t = new MyClass();
t.assign({ visible: true });
//instead t.visible = true;

//or

t.assign({ text: "Something" });
//instead t.text = "something";

//or

t.assign({ text: "Something", visible: false });
//instead t.visible = true; 
//        t.text = "something";

but, I have problems in line this[key] = value; with error:

Index signature of object type implicitly has an 'any' type.

What I need to change or my approach is completely wrong?
It would also be a good solution for setting default properties in constructor when interface is constructor parameter.

Edited:
About entries I really liked them so I am using this code:

//extensions.d.ts
interface Object
{
    entries<T>(o: any): [string, T][];
    entries(o: any): [string, any][];
}
//exntesion.js !!note js not ts
if (!Object.entries)
{
    Object.entries = function* entries(obj)
    {
        for (let key of Object.keys(obj))
        {
            yield [key, obj[key]];
        }
    };
}

Edited 2:

The primary idea was to solve problems for overloading constructor where you could set only desired properties.
Here is the complete code if someone else finds it usable.

interface IMy
{
    prop1?: boolean;
    prop2?: string;
    prop3?: string;
    prop4?: number;
}

class MyClass implements IMy
{
    prop1: boolean = false;
    prop2: string = "";
    prop3: string = "Something";
    prop4: number = 0;

    constructor(properties: IMy)
    {
        this.assing(properties);
    }

    assing(o: IMy): void
    {
        let that = (<any>this);
        for (let key in o)
        {
            if (o.hasOwnProperty(key))
            {
                let value = (<any>o)[key];
                if (typeof value !== "undefined" && typeof that[key] !== "undefined")
                    that[key] = value;
            }
        }
    }

}

let my1 = new MyClass({ prop1: true });
let my2 = new MyClass({ prop2: "SomeText", prop3: "Anything" });
//I set prop2 and prop3
let my3 = new MyClass({ prop4: 10 });    
//I set prop4 (fourth parameter)

console.log(my1, my2, my3);

Answer 1

The error itself comes from the --noImplicitAny compiler option. If you'd remove it, the error would go away. But I believe and it's not a bad thing to have.

You'd need to somehow add a type annotation to key, which seems not to be problematic with in a for .. of loop.

I think the approach is not bad, but you'd need to rewrite iteration over properties a bit differently.

As an aside, I assume you're alse targeting ES6 (for the compiler not to complain about .entries(), which looks like an ES6 feature. It looks like it's for arrays, not objects.

EDIT:

inspired by another SO answer - to make the error go away, you could add a cast to any, like so:

(<any>this)[key] = value;

The above about using .entries() still applies, though.

Answer 2

From TypeScript 2.1 better approach would be with keyof and Mapped Types.

function test()
{
    const my = new MyClass();
    my.assign({ prop1: 3});
}


type MyClassPartial = {
    [P in keyof MyClass]?: MyClass[P];
};

class MyClass
{
    prop1: number;
    prop2: string;
    assign(props: MyClassPartial)
    {
        for (const key of Object.keys(props))
        {
            this[key] = props[key];
        }
    }
}