item和images是两个不同的数组，你在没有明确含义的项目中嵌套了图像。不需要准备所有图像的数组。对于每个项目，您可以使用以下代码找到图像：

item.forEach(i => {
    i.addEventListener('click', () => {
        let img = i.querySelector('img')
        let text = img.outerHTML + i.textContent,
            currentText = select.querySelector('.select__current')
        currentText.innerHTML = text
        select.classList.remove('active')
    })
})

<div class="select">
<div class="select__header">
    <span class="select__current"> <img id="selectCurrencyIamge" src="./img/rus.jpg" alt=""> <span id="selectCurrencyValue">+7</span></span>
    <span class="select__icon"><img src="./img/Stroke.svg" alt=""></span>
</div>
<div class="select__body">
    <div class="select__item"><img src="./img/rus.jpg" alt="">+7</div>
    <div class="select__item"><img src="./img/usa.jpg" alt="">+1</div>
    <div class="select__item"><img src="./img/Flag_of_Turkey.svg.webp" alt="">+90</div>
</div>

let header = document.querySelectorAll('.select__header')
let item = document.querySelectorAll('.select__item')
let select = document.querySelector('.select')
let images = document.querySelectorAll('.select__item img')
 header.forEach(i => {
  i.addEventListener('click', () => {
    i.parentElement.classList.toggle('active')
  })
})
 item.forEach((i, index) => {
i.addEventListener('click', () => {
    images.forEach((el) => {
            currentText = select.querySelector('.select__current');    document.getElementById("selectCurrencyIamge").src=images[index].src;    document.getElementById("selectCurrencyValue").innerHTML=i.textContent;
        select.classList.remove('active')
     
    })
})

}）

授权和简化

const select = document.querySelector('.select');
const currentText = select.querySelector('.select__current');

select.addEventListener('click', (e) => {
  const tgt = e.target;
  const head = tgt.closest('.select__header');
  const body = tgt.closest('.select__body');
  if (head) tgt.parentElement.classList.toggle('active');
  else if (body) {
    currentText.innerHTML = tgt.innerHTML;
  }
})

.select {
  width: 110px;
  position: relative;
}

.select img {
  width: 30px;
}

.select__header {
  border: 1px solid #ccc;
  cursor: pointer;
  display: flex;
}

.select__current {
  font-size: 18px;
  padding: 8px;
}

.select__icon {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-shrink: 0;
  height: 40px;
  width: 15px;
  margin-left: auto;
}

.select__icon img {
  width: 10px;
}

.select__body {
  display: none;
  left: 0;
  right: 0;
  border: 1px solid #ccc;
  position: absolute;
  top: 100%;
  background-color: #fff;
}

.select__item {
  line-height: 24px;
  padding: 8px;
  font-size: 16px;
  cursor: pointer;
}

.select__item:hover {
  background-color: #ccc;
}

.select.active .select__body {
  display: block;
}

<div class="select">
  <div class="select__header">
    <span class="select__current">🇷🇺 +7</span>
    <span class="select__icon"><img src="./img/Stroke.svg" alt=""></span>
  </div>
  <div class="select__body">
    <div class="select__item">🇷🇺 +7</div>
    <div class="select__item">🇺🇸+1</div>
    <div class="select__item">🇹🇷 +90</div>
  </div>
</div>