javascript - 这个方法为什么会报错js for of

Question

这个方法问什么会报错

function fab(max) {
    var count = 0, last = 0, current = 1;

    while(count++ < max) {
        yield current;
        var tmp = current;
        current += last;
        last = tmp;
    }
}

for(var i of fab(10)) {
    console.log(i);
}