javascript - 如何使用生成器函数实现循环数组

Question

今天我想知道在 TypeScript 中提供循环数组的最快方法是什么，如:

['one', 'two', 'three'] 

three 之后的下一个值将是 one，我认为它很适合生成器函数。但是它似乎对我不起作用。以下代码有什么问题？

function* stepGen(){
  const steps = ['one', 'two', 'three'];

  let index = 0;

  if(index < steps.length - 1){
   index++;
  } else {
   index = 0;
  }
  yield steps[index];
}

let gen = stepGen();
console.log(gen.next().value); 
console.log(gen.next().value);
console.log(gen.next().value); // should be 'three'
console.log(gen.next().value); // should be 'one'
console.log(gen.next().value);

Answer 1

您的生成器代码中需要一个循环，否则只会发生一个yield:

function* stepGen(steps){
  let index = 0;
  while (true) {
    yield steps[index];
    index = (index+1)%steps.length;
  }
}

let gen = stepGen(['one', 'two', 'three']); // pass array to make it more reusable
console.log(gen.next().value); 
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);

或者你也可以使用 yield*它从一个可迭代的对象中一个一个地产生值:

function* stepGen(steps){
  while (true) yield* steps;
}

let gen = stepGen(['one', 'two', 'three']);
console.log(gen.next().value); 
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);