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I'm trying to test for an ES6 generator with this code:

thegenerator instanceof Generator

However I keep getting ReferenceError: Generator is not defined

It's also weird because I get this when I treat it as an Array

TypeError: Object [object Generator] has no method 'indexOf'

I'm trying to test for an ES6 generator with this code:

thegenerator instanceof Generator

However I keep getting ReferenceError: Generator is not defined

It's also weird because I get this when I treat it as an Array

TypeError: Object [object Generator] has no method 'indexOf'

• javascript
• arrays
• ecmascript-6

Share Improve this question Follow edited Jan 10, 2016 at 5:46 asked Jan 10, 2016 at 5:38 user2486953user2486953 10

• Can you post a demo to reproduce the problem? – elclanrs Commented Jan 10, 2016 at 5:39
• Type of generators are function. – Ahmet Cetin Commented Jan 10, 2016 at 5:44
• @elclanrs I don't know if that's possible with ES6. But it's just that first one liner. – user2486953 Commented Jan 10, 2016 at 5:47
• Yes, Chrome and FF support generators natively, or try jsfiddle or jsbin with Babel. – elclanrs Commented Jan 10, 2016 at 5:50
• Generators are of type Object – adeneo Commented Jan 10, 2016 at 5:51

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3 Answers 3

Sorted by: Reset to default 4

You can just pare the constructor, as it's inherited it should be the same as a new generator

thegenerator.constructor === (function*(){}()).constructor;

FIDDLE

You can use the constructor.name property to figure out.

function isGenerator(name) {
    return name === 'GeneratorFunction';
}

console.log(isGenerator(gen.constructor.name)); // true
console.log(isGenerator(normal.constructor.name)); // false

Otherwise they are pretty much indistinguishable.

const gen = function*() {};
const normal = function() {};

console.log(gen.constructor); // GeneratorFunction()
console.log(typeof gen); // function
console.log(gen instanceof Function); // true
console.log(gen instanceof Object); // true

console.log(normal.constructor); // Function()
console.log(typeof normal); // function
console.log(normal instanceof Function); // true
console.log(normal instanceof Object); // true

console.log(gen.constructor.name); // 'GeneratorFunction'
console.log(normal.constructor.name); // 'Function'

https://jsfiddle/7gwravha/2/

Try using Object.getPrototypeOf() , .toString()

Object.getPrototypeOf(thegenerator).toString() === "[object Generator]"

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