Construct generator function from array

Question

I am trying to build a generator function from an array. The simplest example would be:

    const array = [1,2,3,4]

    function * createGenerator () {
        array.map(function(elem){
            yield elem
        }
    }

And I would expect:

function * createGenerator () {
        yield 1
        yield 2
        yield 3
        yield 4
    }

Also if I want to add a switch statement like this:

function processServerActions (array) {
    for (let elem in array) {
        switch(elem) {
            case 1:
                yield 1111
            case 2:
                yield 22222
            case 3:
                yield 333333
                yield 444444
            case 4:
                yield 55555
        }
    }

}

But is not working. What am I missing?

Thanks!

several syntax errors pop out...

dandavis
– dandavis

2016-11-03 20:14:45 +00:00
Commented Nov 3, 2016 at 20:14 — dandavis
– dandavis, Commented Nov 3, 2016 at 20:14

Nina Scholz · Accepted Answer · 2016-11-03 20:35:30Z

3

The callback can only return the callback. For yielding the generator function, the yield has to be inside of the function, but outside of a nested callback.

Better you use for ... of for yielding a value.

function* createGenerator() {
    for (let elem of array){
        yield elem;
    }
}  

const array = [1,2,3,4],
      c = createGenerator();

console.log([...c]);

You need for (let elem of array) with of instead of in.

function* createGenerator() {
    for (let elem of array) {
        switch(elem) {
            case 1:
                yield 1111;
                break;
            case 2:
                yield 22222;
                break;
            case 3:
                yield 333333;
                yield 444444;
                break;
            case 4:
                yield 55555;
        }
    }
}

const array = [1,2,3,4],
      c = createGenerator();

console.log([...c]);

edited Nov 3, 2016 at 20:35

answered Nov 3, 2016 at 20:15

Nina Scholz

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1 Comment

Nicolas Over a year ago

Great, and if I would want to add a switch statement, to yield some other thing depending on the number I am getting from the array? (I edited the question to show more details about this)

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