Generator.prototype.throw()
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
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