CODEWITHSUNDEEP
typescripttypescript-typings
Sergio Tx
Sergio Tx

Reputation: 3856

Typescript object property typings

I have a function call like this:

var myVar = myFunction({
    property: 'prop',
    functionProperty() {
         console.log(this.property);
    },
    functionProperty2() {
         this.functionProperty();
    }
});

Is there any way to add typings to the object you are passing to the function without declaring it first?

And another question, is there a way to make this.functionProperty() know that this refers to the object? Working with VSCode when hovering it doesn't recognize the keyword this as the object.

Upvotes: 1

Views: 93

Answers (1)

Titian Cernicova-Dragomir
Titian Cernicova-Dragomir

Reputation: 249466

If you use the compiler option noImplicitThis then this will be typed inside your object literal functions correctly. 

function myFunction<T>(o: T) {

}

var myVar = myFunction({
    property: 'prop',
    functionProperty() {
        console.log(this.property);
    },
    functionProperty2() {
        this.functionProperty();
        this.missing // error

    }
});

If you need more control over the type of this, you can use ThisType which is a special marker for the compiler and will tell the compiler what the type of this will be inside the object literal functions (but this will also require noImplicitAny). 

function myFunction<T>(o: T & ThisType<T & { extra: boolean }>) {

}

var myVar = myFunction({
    property: 'prop',
    functionProperty() {
        console.log(this.property);
    },
    functionProperty2() {
        this.functionProperty();
        this.missing // error
        this.extra //ok
    }
});

Upvotes: 1

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