generator function javascript

1function* idMaker() {
2  var index = 0;
3  while (true)
4    yield index++;
5}
6
7var gen = idMaker();
8
9console.log(gen.next().value); // 0
10console.log(gen.next().value); // 1
11console.log(gen.next().value); // 2
12console.log(gen.next().value); // 3
13// ...

1function* fibonacci() {
2  var a = yield 1;
3  yield a * 2;
4}
5
6var it = fibonacci();
7console.log(it);          // "Generator {  }"
8console.log(it.next());   // 1
9console.log(it.send(10)); // 20
10console.log(it.close());  // undefined
11console.log(it.next());   // throws StopIteration (as the generator is now closed)
12

1function* g(){    //or function *g(){}
2  console.log("First");
3  yield 1;
4  console.log("second");
5   yield 2;
6  console.log("third");
7} 
8let generator=g();
9generator.next();
10generator.next();

1
2function* expandSpan(xStart, xLen, yStart, yLen) {
3    const xEnd = xStart + xLen;
4    const yEnd = yStart + yLen;
5    for (let x = xStart; x < xEnd; ++x) {
6         for (let y = yStart; y < yEnd; ++y) {
7            yield {x, y};
8        }
9    }
10} 
11
12
13//this is code from my mario game I dont think this code is functional

1function* name([param[, param[, ... param]]]) {
2   statements
3}
4

1function* makeRangeIterator(start = 0, end = 100, step = 1) {
2    let iterationCount = 0;
3    for (let i = start; i < end; i += step) {
4        iterationCount++;
5        yield i;
6    }
7    return iterationCount;
8}