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doc: fix vm.Script createCachedData example #44487

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Sep 12, 2022
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doc: fix vm.Script createCachedData example #44487

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27 changes: 25 additions & 2 deletions doc/api/vm.md
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Original file line number Diff line number Diff line change
Expand Up @@ -126,6 +126,16 @@ Creates a code cache that can be used with the `Script` constructor's
`cachedData` option. Returns a `Buffer`. This method may be called at any
time and any number of times.

The code cache of the `Script` doesn't contain any JavaScript observable
states. The code cache is safe to be saved along side the script source and
used to construct new `Script` instances multiple times.

Functions in the `Script` source can be marked as lazily compiled and they are
not compiled at construction of the `Script`. These functions are going to be
compiled when they are invoked the first time. The code cache serializes the
metadata that V8 currently knows about the `Script` that it can use to speed up
future compilations.

```js
const script = new vm.Script(`
function add(a, b) {
Expand All @@ -135,11 +145,14 @@ function add(a, b) {
const x = add(1, 2);
`);

const cacheWithoutX = script.createCachedData();
const cacheWithoutAdd = script.createCachedData();
// In `cacheWithoutAdd` the function `add()` is marked for full compilation
// upon invocation.

script.runInThisContext();

const cacheWithX = script.createCachedData();
const cacheWithAdd = script.createCachedData();
// `cacheWithAdd` contains fully compiled function `add()`.
```

### `script.runInContext(contextifiedObject[, options])`
Expand Down Expand Up @@ -780,6 +793,16 @@ Creates a code cache that can be used with the `SourceTextModule` constructor's
`cachedData` option. Returns a `Buffer`. This method may be called any number
of times before the module has been evaluated.

The code cache of the `SourceTextModule` doesn't contain any JavaScript
observable states. The code cache is safe to be saved along side the script
source and used to construct new `SourceTextModule` instances multiple times.

Functions in the `SourceTextModule` source can be marked as lazily compiled
and they are not compiled at construction of the `SourceTextModule`. These
functions are going to be compiled when they are invoked the first time. The
code cache serializes the metadata that V8 currently knows about the
`SourceTextModule` that it can use to speed up future compilations.

```js
// Create an initial module
const module = new vm.SourceTextModule('const a = 1;');
Expand Down