The throw()
method resumes the execution of a generator by throwing an error into it and returns an object with two properties done
and value
.
Syntax
gen.throw(exception)
Parameters
exception
- The exception to throw. For debugging purposes, it is useful to make it an
instanceof
Error
.
Return value
An Object
with two properties:
done
(boolean)-
- Has the value
true
if the iterator is past the end of the iterated sequence. In this casevalue
optionally specifies the return value of the iterator. - Has the value
false
if the iterator was able to produce the next value in the sequence. This is equivalent of not specifying thedone
property altogether.
- Has the value
value
- Any JavaScript value returned by the iterator. Can be omitted when
done
istrue
.
Examples
Using throw()
The following example shows a simple generator and an error that is thrown using the throw
method. An error can be caught by a try...catch
block as usual.
function* gen() { while(true) { try { yield 42; } catch(e) { console.log('Error caught!'); } } } const g = gen(); g.next(); // { value: 42, done: false } g.throw(new Error('Something went wrong')); // "Error caught!" // { value: 42, done: false }
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Generator.prototype.throw' in that specification. |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
throw | Chrome Full support 39 | Edge Full support 13 | Firefox Full support 26 | IE No support No | Opera Full support 26 | Safari Full support 10 | WebView Android Full support 39 | Chrome Android Full support 39 | Firefox Android Full support 26 | Opera Android Full support 26 | Safari iOS Full support 10 | Samsung Internet Android Full support 4.0 | nodejs
Full support
4.0.0
|
Legend
- Full support
- Full support
- No support
- No support
- User must explicitly enable this feature.
- User must explicitly enable this feature.