在你的示例中，:visible不会工作，因为技术上它仍然没有隐藏，只是 * 真的 * 小。使用not()代替。

更新从你的评论，我假设你想重置计数后5。为此，我们可以使用modulo (or remainder) operator得到一个除法的余数。

let maxPos = 5;

//Select all divs that don't contain your transform style and iterate
//The selector would also work with querySelectorAll natively
$("div:not([style*='transform: scale(0.001)'])").each(function(idx){
  //If maxPos > 0 use the modulo operator to get our position index
  //otherwise don't reset
  let classIdx =  maxPos > 0 ? idx % maxPos + 1 : idx;
  //Add the class dynamically based off the index
  $(this).addClass("POS"+classIdx)
  //Or if you want to one line it:
  //$(this).addClass("POS"+(maxPos > 0 ? idx % maxPos + 1 : idx));
});

/*Just to display the added class name*/
[class^=POS]::after {
  content: 'Class: ' attr(class);
  font-size:0.75em;
  display:inline-block;
  padding-left: 3em;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div>Project 1</div>
<div style="transform: scale(0.001)">Project 2</div>
<div style="transform: scale(0.001)">Project 3</div>
<div>Project 4</div>
<div style="transform: scale(0.001)">Project 5</div>
<div>Project 6</div>
<div>Project 7</div>
<div>Project 8</div>
<div>Project 9</div>
<div>Project 10</div>

有关更多信息，请参阅Attribute Selectors和not() pseudo class

首先：这些并不是“隐藏”的。可见与隐藏引用：Difference between :hidden and :not(:visible) in jQuery
此分类上一篇：

我做了什么（大致）

在这里我做了一些操作你的类和多一点，显示如何选择只是那些（这是你的问题）。注意：如果你点击第二个按钮第二次它得到新的第一个.

$(function() {
  $("#make-obvious-stuff").on('click', function() {
    // select by those with the style transform
    let these = $("[style='transform: scale(0.001)']");
    // now do some stuff with them
    // show how many:
    $(this).after("<div class='found'>Found:" + these.length + "</div>");
    // give class to first one
    these.first().addClass("make-obvious");
    // wrap those NOT the first one; see them do nothing
    these.not().first().wrap("<div class='wrapped'></div>");
    // does nothing:
    these.not().first().show(); // does nothing
    // remove the transform on first one: NOW we see it.
    these.first().css("transform", "");

  });

  $("#do-stuff").on('click', function() {
    // do what was asked: (but this does little perhaps?
    let these = $("[style='transform: scale(0.001)']");
    these.eq(0).addClass('itemPOS1');
    these.eq(1).addClass('itemPOS2');// this overrides the style with !important (that is a bad pattern to adopt)
    these.eq(2).addClass('itemPOS3');
    these.eq(4).addClass('itemPOS4');
  });
})

.make-obvious {
  border: solid lime 1px;
  background-color: #ffdddd;
  padding: 1rem;
}

.wrapped: {
  border: solid blue 2px;
  padding: 2rem;
  background-color: #ddffdd;
}

.found {
  margin: 1rem;
  padding: 1rem;
  border: 1px solid black;
}

.itemPOS1 {
  background-color: #ddddff;
}
.itemPOS2 {
  background-color: #ffddff;
  transform: scale(1)!important;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<h2>basic set</h2>
<div>Project 1</div>
<div>Project 2</div>
<div>Project 3</div>
<div>Project 4</div>
<div>Project 5</div>
<h2>test set filtered:</h2>
<div>Project 1</div>
<div style="transform: scale(0.001)">Project 2</div>
<div style="transform: scale(0.001)">Project 3</div>
<div>Project 4</div>
<div style="transform: scale(0.001)">Project 5</div>
Click me first:
<button id="do-stuff">Do Stuff</button> Click me Second:
<button id="make-obvious-stuff">Make Obvious</button>

你可以这样做（检查控制台）：
说明：
1.我们设置一个从1开始的计数器变量
1.我们每隔div
1.我们检查div是否不具有指定的样式，当发现时，我们使用计数器值应用所需的类，并将计数器递增1。
1.当计数器达到我们的上限（5）时，我们将其设置回1。

const allDivs = document.querySelectorAll("div")
let counter=1;
allDivs.forEach(div=>{
  if (div.style.transform !== "scale(0.001)" ) {
  if(counter<6){
  $(div).addClass('itemPOS' + counter);
  counter++
  }else{
  counter=1;
  $(div).addClass('itemPOS' + counter);
  counter++
  }

  }
  console.log( "class is : " + div.classList[0] + " and style(transform) is : " + div.style.transform )

})

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