Destructuring arguments

e.g :

``` ts
function test({ x, y }: { x: number, y: number }) {
console.log(x, y);
}

test({
x: 1,
y: 2
});
```

with defaults :

``` ts
function test({ x = 123, y = 456 } = {}) {
console.log(x, y);
}

test({
x: 1,
y: 2
});
```

with defaults and type annotation:

``` ts
function test({ x = 123, y = 456 }: { x?: number, y?: number } = {}) {
console.log(x, y);
}

test({
x: 1,
y: 2
});

```

Also https://blog.mariusschulz.com/2015/11/13/typing-destructured-object-parameters-in-typescript

No repository file or test is named. Start by reviewing the destructuring examples in the issue and the linked TypeScript article, then locate the relevant book section. Done means the book explains object-parameter destructuring, defaults, and type annotations with accurate examples.

Written by the indexing model from the issue text.