Generators in JavaScript and TypeScript

Generators within JavaScript (and TypeScript) are similar to C# IEnumerable’s such that you can yield a value multiple times from a generator function (in either JavaScript or TypeScript), i.e.

function* someValues() {
    yield 1;
    yield 2;
    yield 3;
}

or within a TypeScript class we can write

export default class MyClass {
    *someValues() {
       yield 1;
       yield 2;
       yield 3;
    }
}

To use the someValues function we can loop using

for(let i of someValues()) {
    console.log(i);
}

Each item returned is a type of { value, done }, so for example 

var values = someValues();

console.log(values.next());
console.log(values.next());
console.log(values.next());
console.log(values.next());

which would output

{ value: 1, done: false }
{ value: 2, done: false }
{ value: 3, done: false }
{ value: undefined, done: true }