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 whendone
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!'); } } } var g = gen(); g.next(); // { value: 42, done: false } g.throw(new Error('Something went wrong')); // "Error caught!" // { value: 42, done: false }
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Generator.prototype.throw' in that specification. |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) The definition of 'Generator.prototype.throw' in that specification. |
Draft |
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.
Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | 39 | 13 | 26 | No | Yes | 10 |
Feature | Android webview | Chrome for Android | Edge mobile | Firefox for Android | Opera Android | iOS Safari | Samsung Internet |
---|---|---|---|---|---|---|---|
Basic support | Yes | Yes | 13 | 26 | Yes | 10 | Yes |