javascript - 对两个不同的序列使用单个生成器

Question

我无法理解为什么我的代码不能正确执行，我使用一个生成器生成两个不同的序列。

function lerp(a, b, perc) {
    return a + (b - a) * perc;
};

function check_lerp(a, b) {
    if(Math.abs(a - b) > 0.3) return true;
    return false;
};

//lerp generator, given a start and end angle generates angles for back-and forth motion.
//start -> end and then end -> start again.
function *lgen(start, end, perc) {
    let back = false;
    s = start;
    e = end;
    while(1) {
        if(check_lerp(s, e)){
            s = lerp(s, e, perc);
            yield s;
        }
        else if(!back) {
            back = true;
            s = end;
            e = start;
        }
        else break;
    }
}

var first =  lgen(0, 10, 0.1);
var second = lgen(100, 200, 0.1);

console.log(first.next().value);
console.log(second.next().value);
console.log(first.next().value); //should be between 0 and 10 but is 119 (resumes second.next() val.)

知道发生了什么事吗？提前致谢。

Answer 1

只使用局部变量。未声明的变量是全局的。

function lerp(a, b, perc) {
  return a + (b - a) * perc;
};

function check_lerp(a, b) {
  if (Math.abs(a - b) > 0.3) return true;
  return false;
};

//lerp generator, given a start and end angle generates angles for back-and forth motion.
//start -> end and then end -> start again.
function* lgen(start, end, perc) {
  let back = false,
      s = start, // declare and initialize
      e = end;   // declare and initialize
  while (1) {
    if (check_lerp(s, e)) {
      s = lerp(s, e, perc);
      yield s;
    } else if (!back) {
      back = true;
      s = end;
      e = start;
    } else break;
  }
}

var first = lgen(0, 10, 0.1);
var second = lgen(100, 200, 0.1);

console.log(first.next().value);
console.log(second.next().value);
console.log(first.next().value); //should be between 0 and 10 but is 119 (resumes second.next() val.)