AsyncGenerator.prototype.throw()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.
The throw()
method of AsyncGenerator
instances acts as if a throw
statement is inserted in the generator's body at the current suspended position, which informs the generator of an error condition and allows it to handle the error, or perform cleanup and close itself.
Syntax
asyncGeneratorInstance.throw(exception)
Parameters
Return value
If the thrown error is not caught, it will return a Promise
which rejects with the exception passed in.
If the exception is caught by a try...catch
and the generator resumes to yield more values, it will return a Promise
which resolves with an Object
with two properties:
Examples
Using throw()
The following example shows a generator and an error that is thrown using the throw
method. An error can be caught by a try...catch
block as usual.
// An async task. Pretend it's doing something more useful
// in practice.
function sleep(time) {
return new Promise((resolve, reject) => {
setTimeout(resolve, time);
});
}
async function* createAsyncGenerator() {
while (true) {
try {
await sleep(500);
yield 42;
} catch (e) {
console.error(e);
}
}
}
const asyncGen = createAsyncGenerator();
asyncGen.next(1).then((res) => console.log(res)); // { value: 42, done: false }
asyncGen
.throw(new Error("Something went wrong")) // Error: Something went wrong
.then((res) => console.log(res)); // { value: 42, done: false }
Specifications
Specification |
---|
ECMAScript Language Specification # sec-asyncgenerator-prototype-throw |
Browser compatibility
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