Throwing Errors

Throw()

Generator Objects have a throw() method that causes an error to be thrown at the most recent yield statement. The throw() method takes in one argument, which is commonly an Error object.

Notice how throw() affects the Generator function:

    function* genFunc(){

            let a = yield 'a';
            console.log(a); // a = 123
            let b = yield 'b'; //exception is thrown, function exits
            //the code below never occurs because an exception occurred and was uncaught
            console.log(b); 
            let c = yield 'c'; 
            console.log(c); 

            return "finished!"; 

    }

    let genObject = genFunc();

    let w = genObject.next(); // w = Object {value: 'a', done: false}, starts generator function
    let x = genObject.next(123); // x = Object {value: 'b', done: false}
    let y = genObject.throw(new Error("error thrown!")); // thrown() is called, y = undefined
    let z = genObject.next('abc'); // z = undefined