refactor(lang/js): move advanced sections, rework runnable functions

Author: vados-cosmonic

component-model/src/SUMMARY.md

@@ -29,8 +29,10 @@
     - [Other Languages](./language-support/building-a-simple-component/other-languages.md)
   - [Importing and reusing components](./importing-and-reusing-components.md)
     - [Rust](./language-support/importing-and-reusing-components/rust.md)
+    - [Javascript](./language-support/importing-and-reusing-components/javascript.md)
   - [Creating runnable components](./creating-runnable-components.md)
     - [Rust](./language-support/creating-runnable-components/rust.md)
+    - [Javascript](./language-support/creating-runnable-components/javascript.md)
   - [Using WIT resources](./using-wit-resources.md)
     - [Rust](./language-support/using-wit-resources/rust.md)
 - [Running Components](./running-components.md)

component-model/src/creating-runnable-components.md

@@ -2,20 +2,55 @@
 
 This section contains language-specific guides on how to create runnable components.
 
+## Running arbitrary functions from reactor (library-like) components
+
+In practice, any interface that is exported from a WebAssembly component can be run by either:
+
+- Creating a custom host/component that imports and reuses the functionality
+- Using high level generic tooling like `wasmtime run --invoke`
+
+For example, given a WebAssembly component which satisfies the following WIT:
+
+```wit
+{{#include ../examples/tutorial/wit/adder/world.wit}}
+```
+
+Use of the exported `add` function inside the `add` interface requires writing a host or other component that is
+built to import and use that functionality. This is exemplified by the [`example-host` available in this repo][example-host].
+
+Alternatively tooling that works generically over components `wasmtime run --invoke`:
+
+```sh
+wasmtime run --invoke 'add(1, 2)' add.component.wasm
+```
+
+Wasmtime contains code that can generically interpret exports, convert arguments to WebAssembly arguments, and execute
+an existing component dynamically.
+
+[example-host](https://github.com/bytecodealliance/component-docs/blob/main/component-model/examples/example-host/README.md)
+
+## Creating components that behave like binaries
+
+While running arbitrary functions require either a custom host/platform or a dynamic tool like `wasmtime run --invoke`,
+components that are treatable as binaries (i.e. a CLI application) can also be built.
+
 At a high level there are at least two ways to create components that are more like binaries than libraries
-(i.e. that are easy to run from a tool like `wasmtime`):
+(i.e. that are easy to run from a tool like `wasmtime run`):
 
 1. Creating a "command" component
-2. Exporting the `wasi:cli/run` interface
+2. Exporting the [`wasi:cli/run` interface][wasi-cli-run]
 
 This section explores how to do the above in relevant languages.
 
+[wasi-cli-iface-run]: https://github.com/WebAssembly/wasi-cli/tree/main/wit/run.wit
+
 ## Languages
 
 This guide is implemented for various languages:
 
-| Language                                                        |
-|-----------------------------------------------------------------|
-| [Rust](./language-support/creating-runnable-components/rust.md) |
+| Language                                                                    |
+|-----------------------------------------------------------------------------|
+| [Rust](./language-support/creating-runnable-components/rust.md)             |
+| [Javascript](./language-support/creating-runnable-components/javascript.md) |
 
 [docs-wit]: ./design/wit.md

component-model/src/importing-and-reusing-components.md

@@ -19,8 +19,9 @@ The `calculator` component has the following interface:
 
 This guide is implemented for various languages:
 
-| Language                                                            |
-|---------------------------------------------------------------------|
-| [Rust](./language-support/importing-and-reusing-components/rust.md) |
+| Language                                                                        |
+|---------------------------------------------------------------------------------|
+| [Rust](./language-support/importing-and-reusing-components/rust.md)             |
+| [Javascript](./language-support/importing-and-reusing-components/javascript.md) |
 
 [docs-wit]: ./design/wit.md