There are multiple syntaxes for embedding functions in javascript objects, and multiple syntaxes for type annotations. For the purposes of this question, I will refer to them as "type in key" (`in` - Car1, Car3) and "type outside key" (`out` - Car2, Car4) - please let me know if there is a better way to describe them.

Looking at the `.js` output, all I can deduce is:

* Typescript throws no errors for any combination of `in` and `out` between typing and variable assignment
* `this` context is preserved ***only*** when `in` syntax is used for ***both type and variable declaration***
* Therefore `in` syntax must be the "right way" of doing this (???)

What other differences are there, if any, between embedding functions in objects using the various syntax combinations below?

`.ts` file:
-----------

```js
interface Car1 {
    brand: string;
    summary(string): string;
}
interface Car2 {
    brand: string;
    summary: (string) => string;
}
interface Car3 {
    brand: string;
    summary(string): string;
}
interface Car4 {
    brand: string;
    summary: (string) => string;
}

const myFirstCar: Car1 = {
    brand: "Tesla",
    summary(color: string): string {
        return `This car is a ${color} ${this.brand}`;
    },
};
const mySecondCar: Car2 = {
    brand: "Ferrari",
    summary: (color: string) => {
        return `This car is a ${color} ${this.brand}`;
    },
};
const myThirdCar: Car3 = {
    brand: "Porsche",
    summary: (color: string) => {
        return `This car is a ${color} ${this.brand}`;
    },
};
const myFourthCar: Car4 = {
    brand: "Ferrari",
    summary: (color: string) => {
        return `This car is a ${color} ${this.brand}`;
    },
};

const color = "red";

console.log(myFirstCar.summary);
console.log(myFirstCar.summary(color));
console.log(mySecondCar.summary);
console.log(mySecondCar.summary(color));
console.log(myThirdCar.summary);
console.log(myThirdCar.summary(color));
console.log(myFourthCar.summary);
console.log(myFourthCar.summary(color));

```

compiled `.js` file:
--------------------

```js
var _this = this;
var myFirstCar = {
    brand: "Tesla",
    summary: function (color) {
        return "This car is a " + color + " " + this.brand;
    }
};
var mySecondCar = {
    brand: "Ferrari",
    summary: function (color) {
        return "This car is a " + color + " " + _this.brand;
    }
};
var myThirdCar = {
    brand: "Porsche",
    summary: function (color) {
        return "This car is a " + color + " " + _this.brand;
    }
};
var myFourthCar = {
    brand: "Ferrari",
    summary: function (color) {
        return "This car is a " + color + " " + _this.brand;
    }
};
var color = "red";
console.log(myFirstCar.summary);
console.log(myFirstCar.summary(color));
console.log(mySecondCar.summary);
console.log(mySecondCar.summary(color));
console.log(myThirdCar.summary);
console.log(myThirdCar.summary(color));
console.log(myFourthCar.summary);
console.log(myFourthCar.summary(color));

```

Console Output
--------------

```
[Function: summary]
This car is a red Tesla
[Function: summary]
This car is a red undefined
[Function: summary]
This car is a red undefined
[Function: summarizeCar]

```

Edit:

* clarification of different syntax types referred to
* "type inside key", `in`, refers to the syntax used `Car1` and `Car3`
* "type outside key",`out`, refers to the syntax used for `Car2` and `Car4`