根据所选选项的宽度调整选择元素的宽度

Question

我希望 select 元素具有更短的默认选项值的宽度。 当用户选择另一个选项时，select 元素应调整自身大小，以便整个文本始终在元素中可见。

我在Auto resizing the SELECT element under selected OPTION's width问题中找到了解决方案，但它不适用于 bootstrap，我不知道为什么。

这是我的尝试：

 $(document).ready(function() { $('select').change(function(){ $("#width_tmp").html($('select option:selected').text()); // 30 : the size of the down arrow of the select box $(this).width($("#width_tmp").width()+30); }); });

 .btn-select { color: #333; background-color: #f5f5f5; border-color: #ccc; padding:7px; } select { width: 60px; } #width_tmp{ display : none; }

 <link href="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/css/bootstrap.css" rel="stylesheet"/> <link href="//cdnjs.cloudflare.com/ajax/libs/font-awesome/4.3.0/css/font-awesome.css" rel="stylesheet"/> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/js/bootstrap.js"></script> <div class="form-group"> <div class="input-group"> <span class="input-group-btn"> <select class="btn btn-select align-left"> <option>All</option> <option>Longer</option> <option>A very very long string...</option> </select> <span id="width_tmp"></span> </span> <input type="text" class="form-control" placeholder="Search by..."> <span class="input-group-btn"> <button class="btn btn-default" type="button"> <i class="fa fa-search"></i> </button> </span> </div> </div>

Answer 1

出现此问题是因为#width_tmp嵌套在.input-group-btn因此它继承了font-size: 0; 来自引导程序的属性。 因此，元素的计算宽度始终为零：

要解决此问题，只需移动<span id="width_tmp"></span>使其不在输入组内。

---

纯JS解决方案

// resize on initial load
document.querySelectorAll("select").forEach(resizeSelect)

// delegated listener on change
document.body.addEventListener("change", (e) => {
    if (e.target.matches("select")) {
        resizeSelect(e.target)
    }
})

function resizeSelect(sel) {
  let tempOption = document.createElement('option');
  tempOption.textContent = sel.selectedOptions[0].textContent;

  let tempSelect = document.createElement('select');
  tempSelect.style.visibility = "hidden";
  tempSelect.style.position = "fixed"
  tempSelect.appendChild(tempOption);
  
  sel.after(tempSelect);
  sel.style.width = `${+tempSelect.clientWidth + 4}px`;
  tempSelect.remove();
}

jsFiddle和 Stack Snippets 中的演示

 // resize on initial load document.querySelectorAll("select").forEach(resizeSelect) // delegated listener on change document.body.addEventListener("change", (e) => { if (e.target.matches("select")) { resizeSelect(e.target) } }) function resizeSelect(sel) { let tempOption = document.createElement('option'); tempOption.textContent = sel.selectedOptions[0].textContent; let tempSelect = document.createElement('select'); tempSelect.style.visibility = "hidden"; tempSelect.style.position = "fixed" tempSelect.appendChild(tempOption); sel.after(tempSelect); sel.style.width = `${+tempSelect.clientWidth + 4}px`; tempSelect.remove(); }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <select> <option value="2">Some longer option</option> <option value="1">Short option</option> <option value="3">An very long option with a lot of text</option> </select> <select> <option>Short option 2</option> <option>Some longer option 2</option> <option selected>An very long option with a lot of text 2</option> </select>

---

jQuery 插件解决方案

另一种选择是使用插件来处理从头到尾的整个操作。 这是我刚刚提出的一个。

该插件会动态创建和销毁span因此它不会弄乱您的 html。 这有助于分离关注点，并让您将该功能委托给另一个文件，并轻松地跨多个页面重复使用多个元素。

(function($, window){
  $(function() {
    let arrowWidth = 30;

    $.fn.resizeselect = function(settings) {  
      return this.each(function() { 

        $(this).change(function(){
          let $this = $(this);

          // get font-weight, font-size, and font-family
          let style = window.getComputedStyle(this)
          let { fontWeight, fontSize, fontFamily } = style

          // create test element
          let text = $this.find("option:selected").text();
          let $test = $("<span>").html(text).css({
            "font-size": fontSize, 
            "font-weight": fontWeight, 
            "font-family": fontFamily,
            "visibility": "hidden" // prevents FOUC
          });

          // add to body, get width, and get out
          $test.appendTo($this.parent());
          let width = $test.width();
          $test.remove();

          // set select width
          $this.width(width + arrowWidth);

          // run on start
        }).change();

      });
    };

    // run by default
    $("select.resizeselect").resizeselect();                       
  })
})(jQuery, window);

您可以通过以下两种方式之一初始化插件：

1. HTML - 将类.resizeselect添加到任何选择元素：

    <select class="btn btn-select resizeselect "> <option>All</option> <option>Longer</option> <option>A very very long string...</option> </select>

2. JavaScript - 在任何 jQuery 对象上调用.resizeselect() ：

    $("select"). resizeselect ()

jsFiddle和 StackSnippets 中的演示：

 (function($, window){ $(function() { let arrowWidth = 30; $.fn.resizeselect = function(settings) { return this.each(function() { $(this).change(function(){ let $this = $(this); // get font-weight, font-size, and font-family let style = window.getComputedStyle(this) let { fontWeight, fontSize, fontFamily } = style // create test element let text = $this.find("option:selected").text(); let $test = $("<span>").html(text).css({ "font-size": fontSize, "font-weight": fontWeight, "font-family": fontFamily, "visibility": "hidden" // prevents FOUC }); // add to body, get width, and get out $test.appendTo($this.parent()); let width = $test.width(); $test.remove(); // set select width $this.width(width + arrowWidth); // run on start }).change(); }); }; // run by default $("select.resizeselect").resizeselect(); }) })(jQuery, window);

 .btn-select { color: #333; background-color: #f5f5f5; border-color: #ccc; padding:7px; }

 <link href="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/css/bootstrap.css" rel="stylesheet"/> <link href="//cdnjs.cloudflare.com/ajax/libs/font-awesome/4.3.0/css/font-awesome.css" rel="stylesheet"/> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.2/js/bootstrap.js"></script> <div class="form-group"> <div class="input-group"> <span class="input-group-btn"> <select class="btn btn-select resizeselect"> <option>All</option> <option>Longer</option> <option>A very very long string...</option> </select> </span> <input type="text" class="form-control" placeholder="Search by..."> <span class="input-group-btn"> <button class="btn btn-default" type="button"> <i class="fa fa-search"></i> </button> </span> </div> </div>