Struct Promise 

pub struct Promise<T = JsValue> { /* private fields */ }

The Promise object represents the eventual completion (or failure) of an asynchronous operation, and its resulting value.

MDN documentation

Implementations

impl Promise

pub fn new(cb: &mut dyn FnMut(Function, Function)) -> Promise

Creates a new Promise with the provided executor cb

The cb is a function that is passed with the arguments resolve and reject. The cb function is executed immediately by the Promise implementation, passing resolve and reject functions (the executor is called before the Promise constructor even returns the created object). The resolve and reject functions, when called, resolve or reject the promise, respectively. The executor normally initiates some asynchronous work, and then, once that completes, either calls the resolve function to resolve the promise or else rejects it if an error occurred.

If an error is thrown in the executor function, the promise is rejected. The return value of the executor is ignored.

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impl<T> Promise<T>

where T: JsGeneric,

pub fn new_typed<'a>( cb: &ImmediateClosure<'a, dyn FnMut(Function<fn(T) -> Undefined>, Function<fn(JsValue) -> Undefined>) + 'a>, ) -> Promise<T>

where ImmediateClosure<'a, dyn FnMut(Function<fn(T) -> Undefined>, Function<fn(JsValue) -> Undefined>) + 'a>: ErasableGenericBorrow<ImmediateClosure<'static, dyn FnMut(Function<fn(JsValue) -> Undefined>, Function<fn(JsValue) -> Undefined>) + 'static>>, Promise<T>: ErasableGenericOwn<Promise<JsValue>>,

Creates a new Promise with the provided executor cb

MDN documentation

impl Promise

pub fn all(obj: &JsValue) -> Promise

The Promise.all(iterable) method returns a single Promise that resolves when all of the promises in the iterable argument have resolved or when the iterable argument contains no promises. It rejects with the reason of the first promise that rejects.

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impl Promise

pub fn all_iterable<I>( obj: &I, ) -> Promise<Array<<I::Item as Promising>::Resolution>>

where I: Iterable + ErasableGenericBorrow<JsValue>, I::Item: Promising, Promise<Array<<I::Item as Promising>::Resolution>>: ErasableGenericOwn<Promise<Array<<JsValue as Promising>::Resolution>>>,

The Promise.all(iterable) method returns a single Promise that resolves when all of the promises in the iterable argument have resolved or when the iterable argument contains no promises. It rejects with the reason of the first promise that rejects.

MDN documentation

impl Promise

pub fn all_settled(obj: Object) -> Promise

The Promise.allSettled(iterable) method returns a single Promise that resolves when all of the promises in the iterable argument have either fulfilled or rejected or when the iterable argument contains no promises.

MDN documentation

impl Promise

pub fn all_settled_iterable<I>( obj: &I, ) -> Promise<Array<PromiseState<<I::Item as Promising>::Resolution>>>

where I: Iterable + ErasableGenericBorrow<JsValue>, I::Item: Promising, Promise<Array<PromiseState<<I::Item as Promising>::Resolution>>>: ErasableGenericOwn<Promise<Array<PromiseState<<JsValue as Promising>::Resolution>>>>,

The Promise.allSettled(iterable) method returns a single Promise that resolves when all of the promises in the iterable argument have either fulfilled or rejected or when the iterable argument contains no promises.

MDN documentation

impl Promise

pub fn any(obj: &JsValue) -> Promise

The Promise.any(iterable) method returns a single Promise that resolves when any of the promises in the iterable argument have resolved or when the iterable argument contains no promises. It rejects with an AggregateError if all promises in the iterable rejected.

MDN documentation

impl Promise

pub fn any_iterable<I>(obj: &I) -> Promise<<I::Item as Promising>::Resolution>

where I: Iterable + ErasableGenericBorrow<JsValue>, I::Item: Promising, Promise<<I::Item as Promising>::Resolution>: ErasableGenericOwn<Promise<<JsValue as Promising>::Resolution>>,

The Promise.any(iterable) method returns a single Promise that resolves when any of the promises in the iterable argument have resolved or when the iterable argument contains no promises. It rejects with an AggregateError if all promises in the iterable rejected.

MDN documentation

impl Promise

pub fn race(obj: &JsValue) -> Promise

The Promise.race(iterable) method returns a promise that resolves or rejects as soon as one of the promises in the iterable resolves or rejects, with the value or reason from that promise.

MDN documentation

impl Promise

pub fn race_iterable<I>(obj: &I) -> Promise<<I::Item as Promising>::Resolution>

where I: Iterable + ErasableGenericBorrow<JsValue>, I::Item: Promising, Promise<<I::Item as Promising>::Resolution>: ErasableGenericOwn<Promise<<JsValue as Promising>::Resolution>>,

The Promise.race(iterable) method returns a promise that resolves or rejects as soon as one of the promises in the iterable resolves or rejects, with the value or reason from that promise.

MDN documentation

impl Promise

pub fn reject(obj: &JsValue) -> Promise

The Promise.reject(reason) method returns a Promise object that is rejected with the given reason.

MDN documentation

impl Promise

pub fn reject_typed<T>(obj: &JsValue) -> Promise<T>

where Promise<T>: ErasableGenericOwn<Promise<JsValue>>,

The Promise.reject(reason) method returns a Promise object that is rejected with the given reason.

MDN documentation

impl Promise

pub fn resolve<U>(obj: &U) -> Promise<U::Resolution>

where U: Promising + ErasableGenericBorrow<JsValue>, Promise<U::Resolution>: ErasableGenericOwn<Promise<JsValue>>,

The Promise.resolve(value) method returns a Promise object that is resolved with the given value. If the value is a promise, that promise is returned; if the value is a thenable (i.e. has a “then” method), the returned promise will “follow” that thenable, adopting its eventual state; otherwise the returned promise will be fulfilled with the value.

MDN documentation

impl<T> Promise<T>

pub fn catch( &self, cb: &ScopedClosure<'_, dyn FnMut(JsValue)>, ) -> Promise<JsValue>

The catch() method returns a Promise and deals with rejected cases only. It behaves the same as calling Promise.prototype.then(undefined, onRejected) (in fact, calling obj.catch(onRejected) internally calls obj.then(undefined, onRejected)).

MDN documentation

impl<T> Promise<T>

pub fn catch_map<'a, R>( &self, cb: &ScopedClosure<'a, dyn FnMut(T) -> Result<R, JsError>>, ) -> Promise<R::Resolution>

where R: Promising, ScopedClosure<'a, dyn FnMut(T) -> Result<R, JsError>>: ErasableGenericBorrow<ScopedClosure<'static, dyn FnMut(JsValue) -> Result<JsValue, JsError>>>, Promise<R::Resolution>: ErasableGenericOwn<Promise<JsValue>>,

Same as catch, but returning a result to become the new Promise value.

impl<T> Promise<T>

pub fn then<'a>(&self, cb: &ScopedClosure<'a, dyn FnMut(T)>) -> Promise<JsValue>

where ScopedClosure<'a, dyn FnMut(T)>: ErasableGenericBorrow<ScopedClosure<'static, dyn FnMut(JsValue)>>,

The then() method returns a Promise. It takes up to two arguments: callback functions for the success and failure cases of the Promise.

MDN documentation

impl<T> Promise<T>

pub fn then_with_reject<'a, R>( &self, resolve: &ScopedClosure<'a, dyn FnMut(T) -> Result<R, JsError>>, reject: &ScopedClosure<'a, dyn FnMut(JsValue) -> Result<R, JsError>>, ) -> Promise<R::Resolution>

where R: Promising, ScopedClosure<'a, dyn FnMut(T) -> Result<R, JsError>>: ErasableGenericBorrow<ScopedClosure<'static, dyn FnMut(JsValue) -> Result<JsValue, JsError>>>, ScopedClosure<'a, dyn FnMut(JsValue) -> Result<R, JsError>>: ErasableGenericBorrow<ScopedClosure<'static, dyn FnMut(JsValue) -> Result<JsValue, JsError>>>, Promise<R::Resolution>: ErasableGenericOwn<Promise<JsValue>>,

The then() method returns a Promise. It takes up to two arguments: callback functions for the success and failure cases of the Promise.

MDN documentation

impl<T> Promise<T>

pub fn then_map<'a, R>( &self, cb: &ScopedClosure<'a, dyn FnMut(T) -> Result<R, JsError>>, ) -> Promise<R::Resolution>

where R: Promising, ScopedClosure<'a, dyn FnMut(T) -> Result<R, JsError>>: ErasableGenericBorrow<ScopedClosure<'static, dyn FnMut(JsValue) -> Result<JsValue, JsError>>>, Promise<R::Resolution>: ErasableGenericOwn<Promise<JsValue>>,

Alias for then() with a return value. The then() method returns a Promise. It takes up to two arguments: callback functions for the success and failure cases of the Promise.

MDN documentation

impl<T> Promise<T>

pub fn finally(&self, cb: &ScopedClosure<'_, dyn FnMut()>) -> Promise<JsValue>

The finally() method returns a Promise. When the promise is settled, whether fulfilled or rejected, the specified callback function is executed. This provides a way for code that must be executed once the Promise has been dealt with to be run whether the promise was fulfilled successfully or rejected.

This lets you avoid duplicating code in both the promise’s then() and catch() handlers.

MDN documentation

Methods from Deref<Target = Object>

pub fn constructor(&self) -> Function

The constructor property returns a reference to the Object constructor function that created the instance object.

MDN documentation

pub fn has_own_property(&self, property: &JsValue) -> bool

👎Deprecated: Use Object::hasOwn instead.

The hasOwnProperty() method returns a boolean indicating whether the object has the specified property as its own property (as opposed to inheriting it).

MDN documentation

pub fn is_prototype_of(&self, value: &JsValue) -> bool

The isPrototypeOf() method checks if an object exists in another object’s prototype chain.

MDN documentation

pub fn property_is_enumerable(&self, property: &JsValue) -> bool

The propertyIsEnumerable() method returns a Boolean indicating whether the specified property is enumerable.

MDN documentation

pub fn to_locale_string(&self) -> JsString

The toLocaleString() method returns a string representing the object. This method is meant to be overridden by derived objects for locale-specific purposes.

MDN documentation

pub fn to_string(&self) -> JsString

The toString() method returns a string representing the object.

MDN documentation

pub fn to_js_string(&self) -> JsString

The toString() method returns a string representing the object.

MDN documentation

pub fn value_of(&self) -> Object

The valueOf() method returns the primitive value of the specified object.

MDN documentation

Methods from Deref<Target = JsValue>

pub const NULL: JsValue

pub const UNDEFINED: JsValue

pub const TRUE: JsValue

pub const FALSE: JsValue

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.

pub fn is_string(&self) -> bool

Tests whether this JS value is a JS 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.

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>

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

Tests whether this JS value is null

pub fn is_undefined(&self) -> bool

Tests whether this JS value is undefined

pub fn is_null_or_undefined(&self) -> bool

Tests whether this JS value is null or undefined

pub fn is_symbol(&self) -> bool

Tests whether the type of this JS value is symbol

pub fn is_object(&self) -> bool

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

pub fn is_array(&self) -> bool

Tests whether this JS value is an instance of Array.

pub fn is_function(&self) -> bool

Tests whether the type of this JS value is function.

pub fn is_bigint(&self) -> bool

Tests whether the type of this JS value is bigint.

pub fn js_typeof(&self) -> JsValue

Applies the unary typeof JS operator on a JsValue.

MDN documentation

pub fn js_in(&self, obj: &JsValue) -> bool

Applies the binary in JS operator on the two JsValues.

MDN documentation

pub fn is_truthy(&self) -> bool

Tests whether the value is “truthy”.

pub fn is_falsy(&self) -> bool

Tests whether the value is “falsy”.

pub fn loose_eq(&self, other: &JsValue) -> bool

Compare two JsValues for equality, using the == operator in JS.

MDN documentation

pub fn bit_not(&self) -> JsValue

Applies the unary ~ JS operator on a JsValue.

MDN documentation

pub fn unsigned_shr(&self, rhs: &JsValue) -> u32

Applies the binary >>> JS operator on the two JsValues.

MDN documentation

pub fn checked_div(&self, rhs: &JsValue) -> JsValue

Applies the binary / JS operator on two JsValues, catching and returning any RangeError thrown.

MDN documentation

pub fn pow(&self, rhs: &JsValue) -> JsValue

Applies the binary ** JS operator on the two JsValues.

MDN documentation

pub fn lt(&self, other: &JsValue) -> bool

Applies the binary < JS operator on the two JsValues.

MDN documentation

pub fn le(&self, other: &JsValue) -> bool

Applies the binary <= JS operator on the two JsValues.

MDN documentation

pub fn ge(&self, other: &JsValue) -> bool

Applies the binary >= JS operator on the two JsValues.

MDN documentation

pub fn gt(&self, other: &JsValue) -> bool

Applies the binary > JS operator on the two JsValues.

MDN documentation

pub fn unchecked_into_f64(&self) -> f64

Applies the unary + JS operator on a JsValue. Can throw.

MDN documentation

Trait Implementations

impl<T> AsRef<JsValue> for Promise<T>

fn as_ref(&self) -> &JsValue

Converts this type into a shared reference of the (usually inferred) input type.

impl<T> AsRef<Object> for Promise<T>

fn as_ref(&self) -> &Object

Converts this type into a shared reference of the (usually inferred) input type.

impl<T> AsRef<Promise<T>> for Promise<T>

fn as_ref(&self) -> &Promise<T>

Converts this type into a shared reference of the (usually inferred) input type.

impl<T: Clone> Clone for Promise<T>

fn clone(&self) -> Promise<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Promise<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Deref for Promise<T>

type Target = Object

The resulting type after dereferencing.

fn deref(&self) -> &Object

Dereferences the value.

impl<T> ErasableGeneric for Promise<T>

type Repr = JsValue

The singular concrete type that all generic variants can be transmuted on

impl From<JsValue> for Promise

fn from(obj: JsValue) -> Self

Converts to this type from the input type.

impl<T> From<Promise<T>> for JsValue

fn from(obj: Promise<T>) -> JsValue

Converts to this type from the input type.

impl<T> From<Promise<T>> for Object

fn from(obj: Promise<T>) -> Object

Converts to this type from the input type.

impl<T> FromWasmAbi for Promise<T>

type Abi = <JsValue as FromWasmAbi>::Abi

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: Self::Abi) -> Self

Recover a Self from Self::Abi.

impl<'a, T> IntoWasmAbi for &'a Promise<T>

type Abi = <&'a JsValue as IntoWasmAbi>::Abi

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> Self::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl<T> IntoWasmAbi for Promise<T>

type Abi = <JsValue as IntoWasmAbi>::Abi

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> Self::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl<T> JsCast for Promise<T>

fn instanceof(val: &JsValue) -> bool

Performs a dynamic instanceof check to see whether the JsValue provided is an instance of this type.

fn unchecked_from_js(val: JsValue) -> Self

Performs a zero-cost unchecked conversion from a JsValue into an instance of Self

fn unchecked_from_js_ref(val: &JsValue) -> &Self

Performs a zero-cost unchecked conversion from a &JsValue into an instance of &Self.

fn has_type<T>(&self) -> bool

where T: JsCast,

Test whether this JS value has a type T.

fn dyn_into<T>(self) -> Result<T, Self>

where T: JsCast,

Performs a dynamic cast (checked at runtime) of this value into the target type T.

fn dyn_ref<T>(&self) -> Option<&T>

where T: JsCast,

Performs a dynamic cast (checked at runtime) of this value into the target type T.

fn unchecked_into<T>(self) -> T

where T: JsCast,

Performs a zero-cost unchecked cast into the specified type.

fn unchecked_ref<T>(&self) -> &T

where T: JsCast,

Performs a zero-cost unchecked cast into a reference to the specified type.

fn is_instance_of<T>(&self) -> bool

where T: JsCast,

Test whether this JS value is an instance of the type T.

fn is_type_of(val: &JsValue) -> bool

Performs a dynamic check to see whether the JsValue provided is a value of this type.

impl<T> LongRefFromWasmAbi for Promise<T>

type Abi = <JsValue as LongRefFromWasmAbi>::Abi

Same as RefFromWasmAbi::Abi

type Anchor = Promise<T>

Same as RefFromWasmAbi::Anchor

unsafe fn long_ref_from_abi(js: Self::Abi) -> Self::Anchor

Same as RefFromWasmAbi::ref_from_abi

impl<T> OptionFromWasmAbi for Promise<T>

fn is_none(abi: &Self::Abi) -> bool

Tests whether the argument is a “none” instance. If so it will be deserialized as None, and otherwise it will be passed to FromWasmAbi.

impl<'a, T> OptionIntoWasmAbi for &'a Promise<T>

fn none() -> Self::Abi

Returns an ABI instance indicating “none”, which JS will interpret as the None branch of this option.

impl<T> OptionIntoWasmAbi for Promise<T>

fn none() -> Self::Abi

Returns an ABI instance indicating “none”, which JS will interpret as the None branch of this option.

impl<T: JsGeneric> Promising for Promise<T>

type Resolution = T

The type that this value resolves to.

impl<T> RefFromWasmAbi for Promise<T>

type Abi = <JsValue as RefFromWasmAbi>::Abi

The Wasm ABI type references to Self are recovered from.

type Anchor = ManuallyDrop<Promise<T>>

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.

unsafe fn ref_from_abi(js: Self::Abi) -> Self::Anchor

Recover a Self::Anchor from Self::Abi.

impl<T> WasmDescribe for Promise<T>

fn describe()

impl<T> UpcastFrom<Promise<T>> for JsOption<Object>

impl<T, __UpcastTarget0> UpcastFrom<Promise<T>> for JsOption<Promise<__UpcastTarget0>>

where __UpcastTarget0: UpcastFrom<T>,

impl<T> UpcastFrom<Promise<T>> for JsValue

impl<T> UpcastFrom<Promise<T>> for Object

impl<T, __UpcastTarget0> UpcastFrom<Promise<T>> for Promise<__UpcastTarget0>

where __UpcastTarget0: UpcastFrom<T>,