"Utilize Typescript to create a function within a nested object structure

Question

"Utilize Typescript to create a function within a nested object structure

I have a scenario where I am trying to access the foo variable inside the function a of the test object.

class bar {
    private foo: string = "foobar";

    constructor() { /* ... Implementation ... */ }

    fncA(): this {
        // ... implementation 
        console.log(this.foo); // This correctly outputs "foobar"
        const test = {
            "a": function() {
                // ... implementation
            },
            "b": function() {
                console.log(this.foo); // TypeError: this.foo is undefined
            }
        };
        return this;
    }
}

TypeError: this.foo is undefined

It seems like there are some binding problems with the this variable. I am struggling to find the right solution to this issue.

Any help would be greatly appreciated. Thank you in advance.

javascript typescript this

Answer 1

Answer №1

For this specific scenario, a solution could be to define the functions within the test object as arrow functions. This way, they will close over the this keyword instead of having it determined by how they are called:

class bar {
    private foo: string = "foobar";

    constructor() { /* ... Implementation ... */ }

    fncA(): this {
        // ... implementation 
        console.log(this.foo); // this will display "foobar" as expected
        const test = {
            "a": () => {                // ***
                // ... implementation
            },
            "b": () => {                // ***
                console.log(this.foo);
            }
        };
        return this;
    }
}

(It is important to note that while this resolves the TypeScript error regarding this.foo, the test object is not utilized anywhere in the provided code.)

On a side note: It is commonly accepted in JavaScript and TypeScript to capitalize the names of constructor functions. Therefore, it is recommended to use class Bar instead of class bar.

Answer 2

For this specific scenario, a solution could be to define the functions within the test object as arrow functions. This way, they will close over the this keyword instead of having it determined by how they are called:

class bar {
    private foo: string = "foobar";

    constructor() { /* ... Implementation ... */ }

    fncA(): this {
        // ... implementation 
        console.log(this.foo); // this will display "foobar" as expected
        const test = {
            "a": () => {                // ***
                // ... implementation
            },
            "b": () => {                // ***
                console.log(this.foo);
            }
        };
        return this;
    }
}

(It is important to note that while this resolves the TypeScript error regarding this.foo, the test object is not utilized anywhere in the provided code.)

On a side note: It is commonly accepted in JavaScript and TypeScript to capitalize the names of constructor functions. Therefore, it is recommended to use class Bar instead of class bar.

"Utilize Typescript to create a function within a nested object structure

Answer №1

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