feat: FormData support and Request.formData and Response.formData (#1144)

Author: guybedford

documentation/docs/globals/Blob/Blob.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# Blob()
+
+The **`Blob()`** constructor creates a `Blob` object, which represents a file-like object of immutable, raw data.
+
+## Syntax
+
+```js
+new Blob()
+new Blob(array)
+new Blob(array, options)
+```
+
+> **Note:** `Blob()` can only be constructed with `new`. Attempting to call it without `new` throws a `TypeError`.
+
+### Parameters
+
+- `array` _**optional**_
+
+  - : An array of values to include in the `Blob`. These can be [`ArrayBuffer`](../../globals/ArrayBuffer/ArrayBuffer.mdx), [`ArrayBufferView`](../../globals/ArrayBufferView/ArrayBufferView.mdx), [`Blob`](../../globals/Blob/Blob.mdx), or strings. If any of these elements is a [`Blob`](../../globals/Blob/Blob.mdx), its content (and not the object itself) is copied into the Blob being constructed.
+
+- `options` _**optional**_
+
+  - : An object containing optional attributes for the `Blob`.
+    - `type`
+      - : A string indicating the MIME type of the data. The default value is the empty string `""`.
+    - `endings`
+      - : A string indicating how to handle line endings in the data. This can be either `"transparent"` (default) to keep line endings unchanged, or `"native"` to convert line endings to the platform's native line endings (e.g., `\r\n` on Windows).
+
+### Return value
+
+A new `Blob` object containing the specified data.
+
+## Description
+
+`Blob` objects represent data that isn't necessarily in a JavaScript-native format. The `File` interface is based on `Blob`, inheriting its functionality and expanding it to support files on the user's system.
+
+To construct a `Blob` from other non-blob objects and data, use the `Blob()` constructor. To create a blob that contains a subset of another blob's data, use the [`slice()`](../../globals/Blob/prototype/slice.mdx) method.
+
+The `type` property of a `Blob` object will match the MIME type specified in the constructor's `options` parameter, defaulting to an empty string if not specified.

documentation/docs/globals/Blob/prototype/arrayBuffer.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# Blob.arrayBuffer()
+
+The **`arrayBuffer()`** method of the `Blob` interface returns a `Promise` that resolves with an `ArrayBuffer` containing the entire contents of the `Blob` as binary data.
+
+## Syntax
+
+```js
+arrayBuffer()
+```
+
+### Parameters
+
+None.
+
+### Return value
+
+A `Promise` that resolves with an `ArrayBuffer` containing the blob's data.

documentation/docs/globals/Blob/prototype/size.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# Blob.size
+
+The **`size`** read-only property of the `Blob` interface returns the size of the `Blob` in bytes.
+
+## Value
+
+A number representing the size of the `Blob` in bytes.

documentation/docs/globals/Blob/prototype/slice.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# Blob.slice()
+
+The **`slice()`** method of the `Blob` interface creates and returns a new `Blob` object which contains data from a subset of the blob on which it's called.
+
+## Syntax
+
+```js
+slice()
+slice(start)
+slice(start, end)
+slice(start, end, contentType)
+```
+
+### Parameters
+
+- `start` _**optional**_
+  - : The 0-based index of the first byte to include in the new `Blob`. If negative, it refers to an index from the end of the `Blob`. The default value is 0.
+- `end` _**optional**_
+  - : The 0-based index of the first byte that will not be included in the new `Blob`. If negative, it refers to an index from the end of the `Blob`. The default value is `size`.
+- `contentType` _**optional**_
+  - : A string indicating the content type to assign to the new `Blob`. The default value is an empty string.
+
+### Return value
+
+A new `Blob` object containing the specified subset of data.

documentation/docs/globals/Blob/prototype/stream.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# Blob.stream()
+
+The **`stream()`** method of the `Blob` interface returns a `ReadableStream` that can be used to read the contents of the `Blob`.
+
+## Syntax
+
+```js
+stream()
+```
+
+### Parameters
+
+None.
+
+### Return value
+
+A `ReadableStream` that provides the data contained within the `Blob`.

documentation/docs/globals/Blob/prototype/text.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# Blob.text()
+
+The **`text()`** method of the `Blob` interface returns a `Promise` that resolves with a string containing the contents of the blob, interpreted as UTF-8.
+
+## Syntax
+
+```js
+text()
+```
+
+### Parameters
+
+None.
+
+### Return value
+
+A `Promise` that resolves with a string containing the blob's data as a text string. The data is always interpreted as UTF-8.

documentation/docs/globals/Blob/prototype/type.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# Blob.type
+
+The **`type`** read-only property of the `Blob` interface returns the MIME type of the `Blob`.
+
+## Value
+
+A string indicating the MIME type of the `Blob`. If the type cannot be determined, this returns an empty string.

documentation/docs/globals/FormData/FormData.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# FormData()
+
+The **`FormData()`** constructor creates a new `FormData` object.
+
+## Syntax
+
+```js
+new FormData()
+new FormData(form)
+```
+
+> **Note:** `FormData()` can only be constructed with `new`. Attempting to call it without `new` throws a `TypeError`.
+
+### Parameters
+
+- `form` _**optional**_
+  - : An HTML `<form>` element — when specified, the `FormData` object will be populated with the form's current key/value pairs using the name property of each element for the keys and their submitted value for the values. File input elements are handled specially: their values are taken from the files selected by the user in the upload control.
+
+### Return value
+
+A new `FormData` object, pre-populated with form data if the optional `form` parameter was provided.
+
+## Description
+
+The `FormData` interface provides a way to construct a set of key/value pairs representing form fields and their values, which can be sent using methods such as `fetch()`. It uses the same format a form would use if the encoding type were set to `"multipart/form-data"`.
+
+You can also append additional data to the `FormData` object after it's created using its various methods.
+
+A `FormData` object can be used in a number of ways with other APIs:
+
+1. It can be sent with the `fetch()` API
+2. It works seamlessly with the `Request` and `Response` objects - it can be used directly as the body of a `Request` object
+3. It can be obtained from a `Response` object using the `formData()` method
+4. It can be passed directly to the `URLSearchParams` constructor
+
+The transmitted data is in the same format that the form's `submit()` method would use to send the data if the form's encoding type were set to `"multipart/form-data"`.

documentation/docs/globals/FormData/prototype/append.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# FormData.append()
+
+The **`append()`** method of the `FormData` interface appends a new value onto an existing key inside a `FormData` object, or adds the key if it does not already exist.
+
+## Syntax
+
+```js
+append(name, value)
+append(name, value, filename)
+```
+
+### Parameters
+
+- `name`
+  - : The name of the field whose data is contained in `value`.
+- `value`
+  - : The value of the field. This can be a string or a `Blob` (including subclasses such as `File`). If none of these, the value is converted to a string.
+- `filename` _**optional**_
+  - : The filename reported to the server when a `Blob` or `File` is passed as the second parameter. The default filename for `Blob` objects is "blob". The default filename for `File` objects is the file's filename.
+
+### Return value
+
+`undefined`

documentation/docs/globals/FormData/prototype/delete.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# FormData.delete()
+
+The **`delete()`** method of the `FormData` interface removes all key/value pairs with the given name from the `FormData` object.
+
+## Syntax
+
+```js
+delete(name)
+```
+
+### Parameters
+
+- `name`
+  - : The name of the key you want to delete.
+
+### Return value
+
+`undefined`

documentation/docs/globals/FormData/prototype/entries.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# FormData.entries()
+
+The **`entries()`** method of the `FormData` interface returns an iterator allowing iteration through all key/value pairs contained in this object. The iterator yields a new array for each key/value pair, with the first element being the key and the second element being the value.
+
+## Syntax
+
+```js
+entries()
+```
+
+### Return value
+
+An `iterator`.

documentation/docs/globals/FormData/prototype/forEach.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# FormData.forEach()
+
+The **`forEach()`** method of the `FormData` interface executes the provided callback function once for each key/value pair in the `FormData` object.
+
+## Syntax
+
+```js
+forEach(callbackFn)
+forEach(callbackFn, thisArg)
+```
+
+### Parameters
+
+- `callbackFn`
+  - : A function to execute for each entry in the object. The function will be passed the following arguments:
+    - `value`
+      - : The value of the current entry.
+    - `key`
+      - : The key of the current entry.
+    - `formData`
+      - : The `FormData` object being traversed.
+- `thisArg` _**optional**_
+  - : A value to use as `this` when executing `callbackFn`.
+
+### Return value
+
+`undefined`

documentation/docs/globals/FormData/prototype/get.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# FormData.get()
+
+The **`get()`** method of the `FormData` interface returns the first value associated with a given key from within a `FormData` object. If you expect multiple values and want all of them, use the [`getAll()`](../../../globals/FormData/prototype/getAll.mdx) method instead.
+
+## Syntax
+
+```js
+get(name)
+```
+
+### Parameters
+
+- `name`
+  - : The name of the key you want to retrieve.
+
+### Return value
+
+A `FormDataEntryValue` containing the value. If the key does not exist, it returns `null`.

documentation/docs/globals/FormData/prototype/getAll.mdx

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+---
+hide_title: false
+hide_table_of_contents: false
+pagination_next: null
+pagination_prev: null
+---
+# FormData.getAll()
+
+The **`getAll()`** method of the `FormData` interface returns all the values associated with a given key from within a `FormData` object.
+
+## Syntax
+
+```js
+getAll(name)
+```
+
+### Parameters
+
+- `name`
+  - : The name of the key you want to retrieve.
+
+### Return value
+
+An array of `FormDataEntryValue` items containing all values with the given key. If the key doesn't exist, an empty array is returned.