Convert arrow function expression body into a block body.

Add {…} to arrow function

**Arrow functions are a concise syntax that can often replace the regular function syntax.**
For example, `function(x, y) { return x * y }` can be replaced with `(x, y) => { return x * y; }`.

However, arrow functions have different semantics and cannot replace regular functions in all cases.
In particular, the scope of arrow functions (including binding of `this`) is established at creation time.
This difference makes arrow functions unsuitable for using them as methods, constructors, and in `call`, `apply`, and `bind` calls.


Replace function expressions with arrow functions, a more concise syntax.

Convert function to arrow function

Convert property assignments with functions to method declarations.

Convert function to object method

Converts a named function to a const declaration with a function expression.

Convert named function declaration to variable declaration

**Default parameters allow providing default values for function parameters. These default values are used if nothing or `undefined` is passed into the function.**
For example, `function f(p = 42) { ... }` sets `p` to `42` if no value is passed in.

Previous ways of setting default values, for example `p = p || 42` can be converted to default parameters.
This refactoring supports converting the following expressions and variants of them:

- or assignment, e.g. `p = p || 42` or `p ||= 42`
- nullish coalescing operator, e.g. `p = p ?? 42`
- ternary with falsy check on parameter, e.g. `p = p ? p : 42`
- ternary with `null` check, e.g. `p = p == null ? 42 : p` or `p = p != null ? p : 42`
- ternary with `undefined` check, e.g. `p = p === undefined ? 42 : p`
- ternary with `typeof` check, e.g. `p = typeof p === "undefined" ? 42 : p`


Replace default value assignment expressions with default parameter values.

Move default value into parameter

Push a parameter of an immediately-invoked function expressions (IIFEs) or an immediately-invoked arrow functions (IIAFs) into the function body.

Push parameter into IIFE/IIAF

Convert an arrow function block body into an expression body.

Remove {…} from arrow function

Remove immediately-invoked function expressions (IIFEs) and immediately-invoked arrow functions (IIAFs) without parameters.

Remove IIFE/IIAF

Functions and methods are essential building blocks of any non-trivial program. The following code actions make it easier to work with functions, methods, and their parameters:

8 Code Assists for Functions and Methods