[−][src]Struct wasm_bindgen::JsValue

pub struct JsValue { /* fields omitted */ }

Representation of an object owned by JS.

A JsValue doesn't actually live in Rust right now but actually in a table owned by the wasm-bindgen generated JS glue code. Eventually the ownership will transfer into wasm directly and this will likely become more efficient, but for now it may be slightly slow.

Methods

`impl JsValue`[src]

`pub const NULL: JsValue`[src]

The null JS value constant.

`pub const UNDEFINED: JsValue`[src]

The undefined JS value constant.

`pub const TRUE: JsValue`[src]

The true JS value constant.

`pub const FALSE: JsValue`[src]

The false JS value constant.

`pub fn from_str(s: &str) -> JsValue`[src]

Creates a new JS value which is a string.

The utf-8 string provided is copied to the JS heap and the string will be owned by the JS garbage collector.

`pub fn from_f64(n: f64) -> JsValue`[src]

Creates a new JS value which is a number.

This function creates a JS value representing a number (a heap allocated number) and returns a handle to the JS version of it.

`pub fn from_bool(b: bool) -> JsValue`[src]

Creates a new JS value which is a boolean.

This function creates a JS object representing a boolean (a heap allocated boolean) and returns a handle to the JS version of it.

`pub fn undefined() -> JsValue`[src]

Creates a new JS value representing undefined.

`pub fn null() -> JsValue`[src]

Creates a new JS value representing null.

`pub fn symbol(description: Option<&str>) -> JsValue`[src]

Creates a new JS symbol with the optional description specified.

This function will invoke the Symbol constructor in JS and return the JS object corresponding to the symbol created.

`pub fn as_f64(&self) -> Option<f64>`[src]

Returns the f64 value of this JS value if it's an instance of a number.

If this JS value is not an instance of a number then this returns None.

`pub fn is_string(&self) -> bool`[src]

Tests whether this JS value is a JS string.

`pub fn as_string(&self) -> Option<String>`[src]

If this JS value is a string value, this function copies the JS string value into wasm linear memory, encoded as UTF-8, and returns it as a Rust String.

To avoid the copying and re-encoding, consider the JsString::try_from() function from js-sys instead.

If this JS value is not an instance of a string or if it's not valid utf-8 then this returns None.

UTF-16 vs UTF-8

JavaScript strings in general are encoded as UTF-16, but Rust strings are encoded as UTF-8. This can cause the Rust string to look a bit different than the JS string sometimes. For more details see the documentation about the str type which contains a few caveats about the encodings.

`pub fn as_bool(&self) -> Option<bool>`[src]

Returns the bool value of this JS value if it's an instance of a boolean.

If this JS value is not an instance of a boolean then this returns None.

`pub fn is_null(&self) -> bool`[src]

Tests whether this JS value is null

`pub fn is_undefined(&self) -> bool`[src]

Tests whether this JS value is undefined

`pub fn is_symbol(&self) -> bool`[src]

Tests whether the type of this JS value is symbol

`pub fn is_object(&self) -> bool`[src]

Tests whether typeof self == "object" && self !== null.

`pub fn is_function(&self) -> bool`[src]

Tests whether the type of this JS value is function.

Trait Implementations

`impl IntoWasmAbi for JsValue`[src]

`type Abi = u32`

The wasm ABI type that this converts into when crossing the ABI boundary. Read more

`fn into_abi(self, _extra: &mut dyn Stack) -> u32`[src]

`impl<'a> IntoWasmAbi for &'a JsValue`[src]

`type Abi = u32`

The wasm ABI type that this converts into when crossing the ABI boundary. Read more

`fn into_abi(self, _extra: &mut dyn Stack) -> u32`[src]

`impl FromWasmAbi for JsValue`[src]

`type Abi = u32`

The wasm ABI type that this converts from when coming back out from the ABI boundary. Read more

`unsafe fn from_abi(js: u32, _extra: &mut dyn Stack) -> JsValue`[src]

`impl RefFromWasmAbi for JsValue`[src]

`type Abi = u32`

The wasm ABI type references to Self are recovered from.

`type Anchor = ManuallyDrop<JsValue>`

The type that holds the reference to Self for the duration of the invocation of the function that has an &Self parameter. This is required to ensure that the lifetimes don't persist beyond one function call, and so that they remain anonymous. Read more