Struct wasm_bindgen::JsValue
source · pub struct JsValue { /* private fields */ }
Expand description
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.
Implementations
sourceimpl JsValue
impl JsValue
sourcepub fn from_str(s: &str) -> JsValue
pub fn from_str(s: &str) -> JsValue
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.
sourcepub fn from_f64(n: f64) -> JsValue
pub fn from_f64(n: f64) -> JsValue
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.
sourcepub fn from_bool(b: bool) -> JsValue
pub fn from_bool(b: bool) -> JsValue
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.
sourcepub fn symbol(description: Option<&str>) -> JsValue
pub fn symbol(description: Option<&str>) -> JsValue
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.
sourcepub fn from_serde<T>(t: &T) -> Result<JsValue>where
T: Serialize + ?Sized,
pub fn from_serde<T>(t: &T) -> Result<JsValue>where
T: Serialize + ?Sized,
Creates a new JsValue
from the JSON serialization of the object t
provided.
This function will serialize the provided value t
to a JSON string,
send the JSON string to JS, parse it into a JS object, and then return
a handle to the JS object. This is unlikely to be super speedy so it’s
not recommended for large payloads, but it’s a nice to have in some
situations!
Usage of this API requires activating the serde-serialize
feature of
the wasm-bindgen
crate.
Errors
Returns any error encountered when serializing T
into JSON.
sourcepub fn into_serde<T>(&self) -> Result<T>where
T: for<'a> Deserialize<'a>,
pub fn into_serde<T>(&self) -> Result<T>where
T: for<'a> Deserialize<'a>,
Invokes JSON.stringify
on this value and then parses the resulting
JSON into an arbitrary Rust value.
This function will first call JSON.stringify
on the JsValue
itself.
The resulting string is then passed into Rust which then parses it as
JSON into the resulting value.
Usage of this API requires activating the serde-serialize
feature of
the wasm-bindgen
crate.
Errors
Returns any error encountered when parsing the JSON into a T
.
sourcepub fn as_f64(&self) -> Option<f64>
pub fn as_f64(&self) -> Option<f64>
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
.
sourcepub fn as_string(&self) -> Option<String>
pub fn as_string(&self) -> Option<String>
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
.
sourcepub fn as_bool(&self) -> Option<bool>
pub fn as_bool(&self) -> Option<bool>
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
.
sourcepub fn is_undefined(&self) -> bool
pub fn is_undefined(&self) -> bool
Tests whether this JS value is undefined
sourcepub fn is_function(&self) -> bool
pub fn is_function(&self) -> bool
Tests whether the type of this JS value is function
.
Trait Implementations
sourceimpl FromWasmAbi for JsValue
impl FromWasmAbi for JsValue
sourceimpl<'a> IntoWasmAbi for &'a JsValue
impl<'a> IntoWasmAbi for &'a JsValue
sourceimpl IntoWasmAbi for JsValue
impl IntoWasmAbi for JsValue
sourceimpl JsCast for JsValue
impl JsCast for JsValue
sourcefn instanceof(_val: &JsValue) -> bool
fn instanceof(_val: &JsValue) -> bool
instanceof
check to see whether the JsValue
provided is an instance of this type. Read moresourcefn unchecked_from_js(val: JsValue) -> Self
fn unchecked_from_js(val: JsValue) -> Self
sourcefn unchecked_from_js_ref(val: &JsValue) -> &Self
fn unchecked_from_js_ref(val: &JsValue) -> &Self
sourcefn is_instance_of<T>(&self) -> boolwhere
T: JsCast,
fn is_instance_of<T>(&self) -> boolwhere
T: JsCast,
T
. Read moresourcefn dyn_into<T>(self) -> Result<T, Self>where
T: JsCast,
fn dyn_into<T>(self) -> Result<T, Self>where
T: JsCast,
T
. Read moresourcefn dyn_ref<T>(&self) -> Option<&T>where
T: JsCast,
fn dyn_ref<T>(&self) -> Option<&T>where
T: JsCast,
T
. Read moresourcefn unchecked_into<T>(self) -> Twhere
T: JsCast,
fn unchecked_into<T>(self) -> Twhere
T: JsCast,
sourcefn unchecked_ref<T>(&self) -> &Twhere
T: JsCast,
fn unchecked_ref<T>(&self) -> &Twhere
T: JsCast,
sourceimpl RefFromWasmAbi for JsValue
impl RefFromWasmAbi for JsValue
type Anchor = ManuallyDrop<JsValue>
type Anchor = ManuallyDrop<JsValue>
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